JCGO - Java source to C code translator --------------------------------------- version 1.16 (2014-04-29) ------------------------- User's Guide ------------
Use of this software is subject to license terms. This is free software distributed under the GPL license with the GNU Classpath exception. See LICENSE file for more details.
JCGO (pronounced as "j-c-go") is a software application which translates (converts) programs written in Java into platform-independent C code, which could, further, be compiled (by third-party tools) into highly-optimized native code for the target platform and deployed.
JCGO application is a powerful solution that enables your desktop, server-side and embedded/mobile/wireless Java applications to take full advantage of the underlying hardware. In addition, JCGO effectively protects your intellectual property by making your programs when compiled to native code as hard to reverse engineer as if they were written in C/C++.
JCGO consists of the following parts: the translator executables (one for every supported development platform), the JCGO-specific part of the Java runtime environment, the JCGO-specific part of a C runtime environment, the precompiled libraries part, the supplementary and JCGO-specific auxiliary tools, miscellaneous and sample source files, and the accompanying documentation.
Licensing, warranty and trademarks issues
This software and its documentation have been tested and reviewed. Nevertheless, the author makes no warranty or representation, either express or implied, with respect to the software and documentation included with this application. In no event will the author be liable for direct, indirect, special, incidental or consequential damages resulting from any defect in the software or documentation included with this application.
Java (tm) and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc.
All trademarks and copyrights mentioned in this documentation are the property of their respective holders.
The rest of the JCGO is covered by GNU General Public License (GPL), version 2, with a special exception (so called "GNU Classpath exception"), which gives you the right to use it within any other software regardless of the license terms (see exact license information in the header of an open source file).
JCGO may contain a number of third-party open-source materials.
Please read COPYING file carefully for the full licensing information. For any included third-party sources see the license information in the header of that files. For any included libraries in a binary form see licenses supplied in their sources and with the corresponding C compilers.
Official project web site
The JCGO project official web home page is: http://www.ivmaisoft.com/jcgo/
The JCGO development repository web page is: https://github.com/ivmai/JCGO
Thank you for downloading JCGO application - the tool for creation of conventional native code applications using the Java programming language. JCGO takes Java source files as input and translates them into a set of files in the platform-independent C programming language, which is further compiled to a binary executable for your target platform by a standard ANSI C/C++ compiler.
JCGO translator uses some optimization algorithms that allow, together with optimizations performed by a C compiler, the resulting executable code to reach better performance if compared with the traditional Java implementations (based on the Just-In-Time technology).
The produced executable does not contain nor require a Java Virtual Machine to execute, so its resource requirements are smaller than that required by a typical Java VM. This also simplifies the process of deployment and distribution of an application. In addition, the produced native code is highly resistant to reverse engineering and tampering.
JCGO at a glance
Producing a native executable file for your Java application is done in three steps with the JCGO application: generation of C code files from Java source files, compiling these C code files into one or more machine-dependent object files, and linking them all together with C library into a binary executable file.
The JCGO translator (which is, in other words, a "retargetable" optimizing Java-source-to-C static whole-program compiler) transforms the Java source files of your application, the source files of all Java libraries used by your application, the source files of the standard class library (the Java Runtime Environment) and a number of the JCGO-specific Java files together (constituting the "translation set" of Java files) at once into a set of files with optimized (but human-readable) platform-independent ISO/ANSI C code. This transformation is performed on the developer's system, which may differ from the target system of your application. If you need to pack any resource files (only the standard Java property file) into your application then you should convert these resource files into the corresponding Java source files (a special stand-alone utility is supplied within the JCGO application to automate this conversion) beforehand and pass them too as an input to the JCGO translator.
To create a native executable file for your application (processed with the JCGO translator) you need a standard ISO/ANSI C compiler and linker for the target platform (the target hardware and operating system). Since JCGO generates platform-independent C code and uses only a small cross-platform (portable) set of the standard C library functions, there is a large number of platforms supported - based on different CPU architectures (e.g., x86, amd64, ppc, ppc64, ia64, sparc, alpha, mips, i8086, arm, sh, xscale, etc.) and running different Operating Systems (e.g., Windows, FreeBSD, GNU/Linux, Mac OS X (Darwin), Solaris SunOS, OS/2, pure DOS, BeOS, PocketPC/WinMobile/WinCE, or even without OS, etc.).
By using the desired C compiler toolkit, you compile the generated C code files (all at once as a single compilation unit or each file separately) for your Java application together with the JCGO-specific C part of Java runtime. A lot of C macros are provided to customize the compilation process and the resulting executable. Besides, a typical C compiler offers a good set of options to control code optimization and debugging support features.
The linkage step for your application is done by the desired C compiler toolkit in the same way as for a normal C program except that a precompiled Garbage Collector library (either static or dynamic) is linked with it too.
Java compliance and unsupported features
JCGO is compliant with the Java 2 Standard Edition (J2SE) v1.4 platform. JCGO uses GNU Classpath v0.93 core class library.
JCGO does not support Java exception stack tracing. JCGO does not support the features introduced in the 3rd version of the Java Language Specification and J2SE v1.5 platform.
JCGO optimization techniques
JCGO translator itself performs at least the following local and global optimizations:
- unused class, methods and fields elimination;
- marking suitable methods for inlining;
- turning virtual calls into direct ones;
- turning all interface method calls into either virtual or direct ones;
- fields, local variables and parameters reordering;
- runtime checks for null pointer, array index, cast type elimination;
- on-the-stack object allocation;
- performing class initialization at program start-up;
- removing unused class meta-information for "Reflection" API;
- packing characters of Latin-1 strings into byte arrays;
- putting static arrays into program image data sections;
- putting strings, classes and immutable arrays into program image read-only section.
The further optimizations of the code are done by the C compiler you use.
JCGO advantages and drawbacks
JCGO employs the concept of the Ahead-of-Time (static) compilation on the developer's system which gives at least the following advantages over the traditional Java VM runtime interpretation and Just-in-Time (JIT) compilation to the compiled programs:
- faster execution and smaller memory footprint (no code interpretation, no unused class meta-information, large set of local and global optimization, runtime checks elimination, code and read-only data sharing across multiple running program instances);
- shorter start-up time (no class load, no class verification, no JIT, functions and static data reordering for faster executable on-demand loading);
- more performance tuning flexibility (you may choose less program size or more speed, more robustness or more speed);
- native and easier program deployment (a single native executable, no stand-alone Java VM Runtime Environment needed, has own name in the process list, applicability of native code packers, code protectors and custom installer creators);
- better resistance to code decompilation and reverse engineering (the compiled program is as hard to decompile as for a conventional C/C++ program).
These advantages identify, in fact, the goals that may be achieved by applying the JCGO to your application.
The drawbacks of JCGO in respect to the Ahead-of-Time compilation are:
- not cross-platform (native executable is created only for the target system specified at compilation time);
- no runtime-specific optimizations and profiling (all optimizations are done at the developer's host and for the specified CPU model only);
- no support for dynamic applications (all the classes comprising the application must be passed to JCGO and compiled to native code at the developer's host, all functions and fields accessed through the Java "Reflection" API should be generally identified).
JCGO translates Java source files instead of binary Java class files of your application - this gives the following advantages:
- some more optimizations are possible;
- the produced C code is more human-readable;
- no need to have a "javac" tool and to manually compile Java source files to Java class binary files.
The drawback of this approach is:
- full sources of the application and the used libraries are needed (you have to decompile Java class binary files if the required Java source files are missing and, of course, if this is legal by the applicable license).
JCGO translates the sources of an application all at once and a C compiler processes the generated C files all at once. The advantages of "all-at-once" translation and compilation are:
- more global optimizations are possible;
- only needed part of the Java VM runtime is compiled;
- unused classes, methods, fields are all eliminated;
- more methods are possible to inline.
The drawbacks of the "all-at-once" approach are:
- everything should be re-translated to C and recompiled if any Java source is changed;
- code duplication in every application executable file is present (for the Java runtime code and used libraries);
- the JCGO translator and a C compiler use a lot of system resources (CPU and RAM) to do the work.
JCGO translates your Java application to a native executable in 3 steps (to C code first, then to object file, and then to executable file). The "through C" conversion model gives you the following advantages over the direct Java-to-executable conversion model:
- much more portability (JCGO has a wide range of the supported target systems);
- allows you to treat Java application as a normal C one (this means that you have much more control over optimization and code tuning, you have ability to look through, verify, adopt the code in C, have ability to use verified and time-proven C/C++ compilers, and you have the possibility to debug and profile your application with the standard C tools);
- gives you flexibility in linking an application with the Garbage Collector and other third-party libraries (both static and dynamic methods of linking are supported).
The drawbacks of the "through C" approach are:
- you need a C compiler for the target system to succeed;
- the used C compiler (and/or linker) may contain bugs;
- it is harder for you to compile an application (you should known the C programming language and have skills in C compilation and linking, you have to manually invoke the C compiler).
Note, however, that while JCGO produces human-readable C code, this code does not contain comments and is not maintainable (i.e., you cannot really use JCGO for your project to migrate from Java to C).
Note also, as an advantage, that JCGO contains and uses only free open sources (except when an AWT GUI application is translated - Sun J2SE v1.4.2 community sources could be used in this case).
Scope of possible applicability
JCGO is targeted mainly for the following user categories:
- application software developers (to get higher performance, smaller memory footprint and smaller start-up time for an application, to protect the code as an intellectual property, to allow an application to execute on platforms without the Java VM support, to simplify deployment, distribution and installation of an application, to apply time-proven and well-known C/C++ compilation and debugging tools to a Java application);
- hardware device developers (to migrate from C device code to Java, to write new device code in Java with nearly the same performance efficiency as in C, to use Java for 8- and 16-bit CPUs with ROM-able code and small amount of RAM, to reuse existing Java code for small device programming);
- software porting men (to execute existing applications on platforms without a Java VM support);
- software advanced users (to get higher performance for frequently used applications, to run an application in the 64-bit mode).
Development system requirements
At present the JCGO translator itself is built to be executed on any "x86" platform running GNU/Linux or Windows operating system.
The minimal hardware requirements for the JCGO translator are:
- Intel Pentium III 500 MHz CPU (or equivalent);
- 1024 MiB RAM;
- 200 MiB free disk space.
The amount of available real RAM space is critical - you should have at least 200 KiB per every class included in the "translation set" in average, otherwise the performance of the JCGO translator significantly degrades.
Operating System requirement for the JCGO translator is (one of):
- Microsoft Windows 2000 or higher (to run "jcgo.exe" on Win32);
- GNU/Linux OS based on Kernel 2.6 or higher (to run Linux version of "jcgo");
- Sun JRE 1.4 or higher (to run "jcgo.jar" as an alternative to Windows and Linux native binary versions of the JCGO translator).
Other development platforms and operating systems could be supported in the future. Note also, that the target platform of a translated application does not depend of the development platform used to run the JCGO translator.
Note about running "jcgo.jar": translation of a big application requires a big stack, so please pass "-Xss" option to JVM with a reasonable value.
Required knowledge and skills
To use the JCGO translator successfully you should generally be familiar with the C programming language and have adequate skills in the compilation area with the C compiler you choose to use for the target platform.
It is also supposed that you know the name of the class with the entry point of the application you translate, the names of all the classes accessed dynamically from the application, the fully-qualified names of all the methods and fields accessed from the application through the Java "Reflection" API.
To start using the JCGO application you need to download the JCGO distributive files and install it successfully.
The following files constitutes "the JCGO distributive files":
- jcgo-src-1_XX.tar.bz2 (the source files used by JCGO and by a C compiler);
- jcgo-lib-1_XX.tar.gz (the auto-generated Java files used by JCGO, precompiled libraries and auxiliary executables for the supported platforms, as well as the JCGO translator executable for a Java VM);
- jcgo-bin-win32-x86.zip (the JCGO translator executable for Windows development host, optional file);
- jcgo-bin-1_XX-linux-x86.tar.gz (the JCGO translator executable for Linux/x86 development host, optional file);
- classpath-0.93.tar.gz (the GNU Classpath - Essential Libraries for Java).
Note: version 0.93 of the GNU Classpath is the only supported version - its later versions are incompatible with JCGO currently.
In addition, in case you need a custom-specific Garbage Collector (GC) library (e.g., for a specific target platform) which is not among the precompiled libraries, then its sources should be downloaded too and, then, compiled manually as required. At present, only two GC libraries are supported:
- Boehm-Demers-Weiser Conservative GC (BDWGC, BoehmGC) version 7.2 or later (with built-in or external libatomic_ops library);
- TinyGC (Tiny Garbage Collector) - a binary-compatible small alternative to Boehm GC (normally, should be used only for targets where Boehm GC is not supported or is unappropriated).
To manually compile the desired GC library, please download gc-7.2.tar.gz (or newer) for Boehm GC, or tinygc-2_5.tar.bz2 (or newer) for TinyGC.
The exact links to the distributive files (and their exact names for the current JCGO version) are provided at the JCGO official web home page.
To compile an SWT GUI application, you will need the corresponding (i.e., for the required target platform) SWT library sources (of version 3.5 or newer - please refer to reflgen/swt.dat for the exact information of the supported versions).
To compile an application which uses Sun Javax Comm API, you will need either RXTX library sources (version 2.2) or the original Sun Java Communications API library sources.
To compile an application that accesses OS API via JNA, you will need JNA (Java Native Access) library sources (version 3.2.7).
Note also, that you need some more distributive files to translate an AWT GUI application (e.g., with Sun Win32/X11 AWT back-ends) or an AWT/SWT application which uses Java Sound API, or an SQL application that uses Sun JDBC-ODBC bridge:
- jcgo-sunawt-lib-1_XX.tar.gz (the JCGO-SUNAWT auto-generated Java files used by the JCGO translator and precompiled import libraries);
- jcgo-sunawt-linux-x86-1_00.tar.gz (JCGO-SUNAWT runtime binary re-distributive pack for GNU Linux/x86 targets);
- jcgo-sunawt-solaris-x86-1_00.tar.gz (JCGO-SUNAWT runtime binary re-distributive pack for Solaris SunOS/x86 targets);
- jcgo-sunawt-win32-x86-1_00.7z (JCGO-SUNAWT runtime binary re-distributive pack for Windows/x86 targets);
- j2sdk-1_4_2-src-scsl.zip (Sun J2SDK v1.4.2 SCSL sources);
- src.zip from the Sun J2SE v1.4.2_19 SDK (Sun Java core API class sources).
JCGO also supports SQLite database connectivity via SqliteJDBC library.
Entirely for the purpose of the distributive files unpacking, you need some tar+gz/bz2 unpacker tool (e.g., tar and ungzip/bzip2 for Unix-like OS, or "7-Zip" for Windows).
Before installing the current version of the JCGO, please completely remove the previous one installation (if you have any).
Then, please extract the JCGO distributive files (using an unpacker tool of your choice) into the "JCGO home" (base) installation folder preserving the directory structure. The recommended name for the JCGO home is "C:\JCGO" on Windows ("/usr/share/JCGO" on Unix-like system), but you are free to use any other folder (directory) for it.
For AWT GUI applications translation, as a special exception (for the above unpacking rule), j2sdk-1_4_2-src-scsl.zip should be unpacked to the newly-created "contrib/j2sdk-1_4_2-src-scsl" folder (of the "JCGO" installation folder) and src.zip from the Sun J2SE v1.4.2_19 SDK - to "contrib/j2sdk1.4.2_19/src", respectively.
Note: at the end of the installation process it is better to protect the entire JCGO installation folder and all its contents from an accidental modification (never add, delete, or modify files within the JCGO application - if you need to use a modified version of a source file then copy it to your project first), so please set "read-only" access to the entire JCGO installation folder and its subfolders (if this protection mechanism is supported by the File System).
JCGO home folder contents
After you complete the JCGO installation process, the JCGO home folder contents are as follows:
- "auxbin" - the JCGO auxiliary tools ("GenRefl", "JPropJav" and "TraceJni" utilities);
- "classpath-0.93" - the unpacked contents of the GNU Classpath ("Essential Libraries for Java") distributive file;
- "contrib" - folder for 3rd-party content used by JCGO (bdwgc, tinygc, swt, j2sdk-1_4_2-src-scsl, j2sdk1.4.2_19/src, etc.);
- "dlls" - precompiled dynamic-link (shared object) libraries (for the supported platforms);
- "examples" - several simple Java samples (like "Hello world") to translate;
- "goclsp" - a set of JCGO-specific partial replacements and fixes for GNU Classpath;
- "include" - the JCGO C core runtime (compiled together with the output of the JCGO translator);
- "jnidload" - the source for creating JCGO-specific static trampolines with distinctive names for multiple dynamically-loaded "JNI_OnLoad" and "JNI_OnUnload" functions (for the case when these functions are residing in multiple dynamic libraries but used together);
- "jtrsrc" - the JCGO translator source;
- "libs" - precompiled libraries (for "x86" and "amd64" platforms only, might be used by a C linker);
- "minihdr" - minimal subset of the standard ISO/ANSI C compiler header files sufficient to compile the JCGO C core runtime and native back-ends (useful only for non-standard C runtime environments);
- "miscsrc" - miscellaneous C and Java sources ("JAWT" stub shared library source, "JPropJav" utility source, "T-PThread" library source and header, "WinMain" wrapper source);
- "mkjcgo" - scripts to verify JCGO Java source (using JDK), generate contents of "rflg_out", and rebuild "auxbin", "libs", jcgo.jar/exe;
- "native" - the JCGO C native back-ends (file I/O, network I/O, process execution, OS-specific properties retrieval);
- "reflgen" - JNI method and field reflection usage data and the sources of the JCGO tools for handling the reflection usage data;
- "rflg_out" - the addendum Java source files used by the JCGO translator (generated automatically by "JPropJav" utility from goclsp/clsp_fix/resource, classpath-0.93/resource, and by "GenRefl" utility from reflgen/*.dat files);
- "COPYING" - GNU General Public License;
- "LICENSE" - JCGO software license agreement;
- "README" - the JCGO "read me" and documentation (this file);
- "README_QUICK.txt" - the JCGO quick start tips (for Windows and Linux);
- "Samples" - C compilation samples;
- "jcgo" - the JCGO translator executable (for GNU/Linux on x86 host);
- "jcgo.exe" - the JCGO translator executable (for Win32 host);
- "jcgo.jar" - the JCGO translator executable (for Java VM);
- "stdpaths.in" - response file (containing the "core" source paths) for the JCGO translator;
- "sawt_out" - the precompiled (generated) parts of the additional "JCGO-SUNAWT" pack (distributed separately);
- "sunawt" - the sources of the additional "JCGO-SUNAWT" pack (optional) integrating the Sun J2SE v1.4.2 AWT/JSound/SQL front-ends.
JCGO translator command-line arguments
The JCGO translator itself ("jcgo") is a command-line tool. It accepts the following arguments:
- optional "verbose mode" switch (-v);
- optional output existing folder name switch (-d
) for the generated ".c" and ".h" files to put in (otherwise, "jcgo_Out" folder in the current folder is created and used);
- the full name of the class with "main(String)" method of the application to translate;
- source paths list specifier switch (-sourcepath
or -src for short) for the translator to get Java source files from (notes: the order of paths is important; it is possible to use "$~" as a path prefix meaning the JCGO home (installation) folder; the current folder is always implicitly added to the end of the specified list; it is also possible to use "conditional" paths, in the form of /$% , meaning that the specified source path should be used only to search for the designated class or classes within the designated package);
- optional additional full class names (for the classes used dynamically via "Class.forName()" calls or through the Java "Reflection" API, including Proxy classes);
- optional command (-r
) to force particular members reflection for a given class or for all classes (of the "translation set") inside a given package (flags specifier: [p|[[p]c][g|[p]m][[p]f]], where flag symbol 'c' means reflect all constructors (if with 'p' prefix then only public entities), 'g' - reflect all declared public non-static getter and setter methods, ['p']'m' - reflect all declared [public] methods, ['p']'f' - reflect all declared [public] fields, single 'p' flag is equivalent to "pcpmpf" specifier, and the flags omission has the same meaning as "cmf" one);
- optional "response" file (@
) for user convenience containing optional additional full class names (one per line), optional source paths list specifier switches ("$~" prefix could be used here too), and optional "-r" commands.
Translating first sample application
The sample conversion of "Hello world" application on Windows and Unix-like development hosts (for the same targets) is provided bellow. It is assumed that the JCGO software is installed into its recommended folder. It is also assumed that "C:\MyProject" ("/home/user/MyProject" on Unix) folder exists, in which the resulting "hello.exe" ("hello" on Unix) native executable file would be put.
For Windows development host and target ("MinGW" C/C++ compiler is used here):
cd C:\MyJcgoProjects mkdir .\Hello C:\JCGO\jcgo -d .\Hello -sourcepath $~\examples\simple Hello @$~\stdpaths.in gcc -IC:\JCGO\include -IC:\JCGO\include\boehmgc -IC:\JCGO\native -DJCGO_FFDATA -o hello .\Hello\Main.c C:\JCGO\libs\x86\mingw\libgc.a
For Linux (on x86) development host and target:
cd /home/user/MyJcgoProjects mkdir ./Hello /usr/share/JCGO/jcgo -d ./Hello -sourcepath $~/examples/simple Hello \ @$~/stdpaths.in gcc -I /usr/share/JCGO/include -I /usr/share/JCGO/include/boehmgc \ -I /usr/share/JCGO/native -fwrapv -DJCGO_UNIX -D_IEEEFP_H \ -DJCGO_UNIFSYS -o hello Hello/Main.c -lm \ /usr/share/JCGO/libs/x86/linux/libgc.a
Appendix A: The core source paths for the JCGO translator
goclsp/clsp_asc - include only to use only Latin-1/UTF-8 in streams; goclsp/clsp_fix - normally should be included (Classpath fixes); goclsp/clsp_ldr - normally should be included; goclsp/clsp_pgk - include only to use Gtk GNU AWT back-end; goclsp/clsp_pqt - include only to use Qt GNU AWT back-end; goclsp/clsp_res - must be always included; goclsp/fpvm - include only to redirect Math to StrictMath methods; goclsp/vm - must be always included (VM-specific classes); goclsp/vm_str - normally should be included (packed strings support); rflg_out - normally should be included; classpath-0.93 - must be always included ("Java essential" classes); classpath-0.93/external/relaxngDatatype - normally should be included; classpath-0.93/external/sax - normally should be included; classpath-0.93/external/w3c_dom - normally should be included.
Appendix B: Environment variables recognized by the JCGO runtime
LOGNAME or USER, or USERNAME - "user.name" property ("anonymous" by default); USERLANG - "user.language" property ("en" by default); USERCTRY - "user.region" property ("US" by default); CODEPAGE - "file.encoding" property ("ISO8859_1" by default); CONSOLE_CODEPAGE - alternate encoding for the console output (stdout/stderr); UNICODE_ENCODING - "sun.io.unicode.encoding" property (either "UnicodeLittle" or "UnicodeBig"); PROCESSOR_ARCHITECTURE or MACHTYPE, or HOSTTYPE - "os.arch" property ("x86" by default); NUMBER_OF_PROCESSORS - number of available processors (1 by default); HOME or HOMEPATH, or USERPROFILE - "user.home" property; TMP or TMPDIR, or TEMP - "java.io.tmpdir" property; PROG_JAVA_HOME - explicit (non-default) "java.home" property; CLASSPATH - for "java.class.path" property; CLASSPATH_HOME - "gnu.classpath.home" property; LD_LIBRARY_PATH and PATH - for "java.library.path" property; PATHEXT - pathlist of valid non-Unix program extensions (e.g., ".EXE;.BAT"); TZ=zzz[+/-]d[d][lll] - time zone information (for "user.timezone" property); JAVA_PROPS - space-separated list of custom Java properties (-Dname=value); NO_TIME_HIGH_RESOLUTION - do not use Win32 system timer resolution switching; STDERROUT_LOGFILE - file name for the redirected stderr/stdout (if turned on); USE_UNICODE_API - explicitly specify whether to use Unicode system API where possible (if allowed) or use its ASCII (multibyte) variant ("0" to use ASCII).
Appendix C: Environment variables recognized by the Garbage Collector
GC_DONT_GC - turn off garbage collection; GC_ENABLE_INCREMENTAL - turn on incremental garbage collection mode (may not work correctly on some platforms); GC_DISABLE_INCREMENTAL - disable incremental garbage collection mode explicitly turned on by an application; GC_PRINT_STATS - turn on statistic printing on every garbage collection; GC_ALL_INTERIOR_POINTERS - turn on "all-interior-pointers" collector mode; GC_IGNORE_GCJ_INFO - ignore the GCJ-style type descriptors (if supported); GC_FORCE_UNMAP_ON_GCOLLECT - force immediate memory unmapping (if supported) on explicitly-initiated garbage collections; GC_INITIAL_HEAP_SIZE - set initial heap size (in bytes); GC_MAXIMUM_HEAP_SIZE - set maximum heap size (in bytes); GC_FREE_SPACE_DIVISOR - change the default trade-off between garbage collection and heap growth; GC_PAUSE_TIME_TARGET - set the desired garbage collection maximal pause time (incremental collection time limit, in milliseconds); GC_UNMAP_THRESHOLD - change the default "threshold" value (if supported) for the garbage collector free blocks unmapping ("0" to disable heap shrinking); GC_MARKERS - explicitly set the number of parallel "marker" threads (if the garbage collector supports parallel marking).
Appendix D: C macros used to control compilation
/ Include "config.h" file /
/ Allow Win32 API usage where necessary /
/ Allow OS/2 platform API usage where necessary /
/ Only if JCGO_THREADS is defined, and JCGO_OS2 and JCGO_WIN32 are not defined: use Solaris SunOS native threads (instead of POSIX threads) /
/ Only if JCGO_THREADS is defined: all threads are allowed to be running fully parallel (otherwise, the threads are non-preemptive except for I/O operations) /
/ Only if JCGO_THREADS and JCGO_PARALLEL are defined: do not use atomic fetch() and store() operations to access Java volatile fields (i.e., treat Java "volatile" access modifier as C one) /
/ Only if JCGO_THREADS is defined: assume that the standard C library is not thread-safe (i.e., C system calls are non-reentrant ones) /
/ Only if JCGO_NOFP is not defined: floating-point variables have the reversed byte-order (the opposite to the order of bytes in an integer variable) /
/ Only if JCGO_NOFP is not defined: allow advanced math functions (cbrt, expm1, floorf, fmodf, log1p) usage where necessary /
/ Only if JCGO_NOFP is not defined: assume that C floating-point division and comparison operations work exactly in accordance to the corresponding IEEE standard /
/ Only if JCGO_NOFP is not defined: assume C math.h functions behavior match Java Math class methods specification /
/ Define (or allow to define if used for compiling C files of the JCGO "native" library) Unicode "wmain" function as the program entry point (instead of "main") /
/ Only if JCGO_NATSEP is not defined: use Unicode (wchar_t) functions of the file API (of the standard C library) where appropriate (otherwise, only ASCII (multibyte) functions are used) /
/ Only if JCGO_NATSEP is not defined and JCGO_SYSWCHAR is defined: choose whether to use Unicode or ASCII (multibyte) functions of the file API (of the standard C library) at run-time (useful for Win32 platform) /
/ Only if JCGO_NATSEP and JCGO_UTFWCTOMB are not defined: use mbstowcs() and wcstombs() (instead of mbtowc() and wctomb(), respectively) for the multibyte-to-Java and Java-to-multibyte string conversions (useful for WinCE platforms) /
/ Only if JCGO_NATSEP is not defined: assume native multi-byte encoding is UTF-8 (useful if mbtowc/wctomb and mbstowcs/wcstombs are missing) /
/ Only if JCGO_NATSEP is not defined: get some Java system properties using Win32 API directly (useful for WinCE platforms) /
/ Only if JCGO_NATSEP is not defined: use Win32 file I/O API directly (useful for WinCE platforms) /
/ Use C "stdout" instead of "stderr" file descriptor for the Java "System.err" stream (and for fatal runtime errors outputting) /
/ Only if JCGO_NOFILES is not defined: redirect (or allow to redirect if used for compiling C files of the JCGO "native" library) C "stderr" (and "stdout" if JCGO_ERRSTDOUT is defined too) stream to ".log" file (only if "STDERROUT_LOGFILE" environment variable is set specifying the log file name or if the executable-name-based log file already exists) /
/ Only if JCGO_ERRTOLOG is defined: force C "stderr" (and "stdout" if JCGO_ERRSTDOUT is defined too) stream redirection (the log file will be created at the program start-up) /
/ Only if JCGO_NATSEP, JCGO_NOFILES and JCGO_WINFILE are not defined: use _findfirst/_findnext/_findclose with handle and _finddata_t data structure for directory scanning /
/ Only if JCGO_NATSEP, JCGO_NOFILES and JCGO_WINFILE are not defined: use findfirst/findnext with ffblk data structure for directory scanning (otherwise, opendir/readdir/closedir are used if JCGO_FFDATA and JCGO_FFDOS are not defined) /
/ Only if JCGO_NATSEP, JCGO_NOFILES and JCGO_WINFILE are not defined: use _dos_findfirst/_dos_findnext with find_t data structure for directory scanning (only if JCGO_FFDATA and JCGO_FFBLK are not defined) /
/ Only if JCGO_NATSEP, JCGO_NOFILES and JCGO_WINFILE are not defined: use file I/O functions with large-file support /
/ Only if JCGO_NATSEP, JCGO_NOFILES, JCGO_UNIX and JCGO_WINFILE are not defined, and JCGO_LARGEFILE is defined: use _chsize_s() file I/O API call (instead of chsize() or SetEndOfFile() ones) /
/ Only if JCGO_NATSEP is not defined: use Unix-style file naming conventions (target for Unix platform) /
/ Only if JCGO_NATSEP and JCGO_UNIFSYS are not defined: target for a single-root file system (required for WinCE platforms) /
/ Only if JCGO_NATSEP and JCGO_NOFILES are not defined, and JCGO_UNIFSYS is defined: target the JCGO "native" library for ancient Mac OS (Darwin) platforms /
/ Only if JCGO_NATSEP and JCGO_WINFILE are not defined, and JCGO_EXEC is defined: use Unix process execution conventions (target for Unix platform) /
/ Only if JCGO_NATSEP is not defined: allow execution (spawning) of child processes /
/ Only if JCGO_NATSEP is not defined: allow Internet networking capabilities to be used /
/ Only if JCGO_NATSEP is not defined, and JCGO_INET and JCGO_WIN32 are defined: use old WinSock v1.1 interface (instead of WinSock v2.2) /
/ Only if JCGO_NATSEP and JCGO_WIN32 are not defined, and JCGO_INET is defined: use GNU-style (BSD) gethostbyaddr_r() and gethostbyname_r() reentrant functions (otherwise, non-reentrant variants of these functions are used if JCGO_SYSVNETDB is not defined) /
/ Only if JCGO_NATSEP, JCGO_WIN32 and JCGO_GNUNETDB are not defined, and JCGO_INET is defined: use SysV-style (Solaris SunOS) gethostbyaddr_r() and gethostbyname_r() reentrant functions (otherwise, non-reentrant variants of these functions are used) /
/ Only if JCGO_NATSEP, JCGO_NOTIME and JCGO_WINFILE are not defined: use clock_gettime(CLOCK_MONOTONIC) to obtain nanoTime() value if possible; only if JCGO_THREADS is defined, and JCGO_WIN32 and JCGO_OS2 are not defined: use clock_gettime(CLOCK_REALTIME) instead of gettimeofday() for timed wait /
/ Only if JCGO_NATSEP is not defined: do not use any C time-related functions /
/ Only if JCGO_NATSEP is not defined: do not provide any access to the underlying file system /
/ Only if JCGO_NATSEP and JCGO_NOFILES are not defined: assume the underlying file system has no concept of a current working directory /
/ Only if JCGO_NATSEP, JCGO_NOFILES, JCGO_NOTIME and JCGO_WINFILE are not defined: do not use C "utimbuf" struct and utime() system call /
/ Only if JCGO_NATSEP and JCGO_NOTIME are not defined: do not treat tv_sec value returned by gettimeofday() and ftime() as unsigned /
/ Only if JCGO_NATSEP and JCGO_NOFILES are not defined: do not use realpath() C library call /
/ Only if JCGO_NATSEP is not defined: do not query system name and release version from OS /
/ Do not print any message on fatal runtime errors /
/ Compile every produced C file separately /
/ Do not compile C files of the JCGO "native" library /
/ Do not support and use Java Native Interface (JNI) /
/ Only if JCGO_NOJNI is not defined: do not support JNI_CreateJavaVM() and AttachCurrentThread() of JNIInvokeInterface /
/ Only if JCGO_CHKCAST or JCGO_INDEXCHK, or JCGO_SFTNULLP, or JCGO_HWNULLZ is defined: abort execution (with the corresponding "assertion violated" message) instead of throwing array-index-out-of-bounds, array-store, class-cast and null-pointer exceptions by VM runtime /
/ Abort the application (on JCGO runtime fatal error) via abort() instead of exit(-1) call. /
/ Enable Java assertions; it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
/ Only if JCGO_STDCLINIT is not defined: turn on class proper initialization order checking; it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
/ Force index checking for every array access; it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
/ Force type checking for all class cast operations and for all object arrays element storing; it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
/ Use (force) explicit software null-pointer dereference checking (instead of using hardware pointer checking support); it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
/ Only if JCGO_SFTNULLP and JCGO_NOSEGV are not defined: always try to dereference an object pointer with zero (or nearly zero) offset first (thus allowing hardware null-pointer dereference checking even if it is limited); it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
/ Do not use SIGSEGV and SIGBUS signals by VM runtime (disable hardware null-pointer dereference checking) /
/ Do not change default handlers for SIGINT and SIGTERM signals /
/ Use Unix platform basic API /
/ Produce code supporting multi-threaded execution /
/ Use the standard class on-demand initialization (otherwise, all classes are initialized at program start-up); it should be used (at least) when the JCGO translator warns that it cannot determine proper initialization order for one or more classes /
/ Use Structured Exception Handling (SEH) instead of setjmp() to implement Java exception handling (works only if jumping out of a __finally block has Java-like behavior during termination handling) /
/ Use C int (instead of C unsigned char) type for the Java boolean type (note that JNI is affected too, so JCGO_BOOLINT should not be normally defined if JCGO_NOJNI is not defined) /
/ Use extended C int8, int16, int32, int64 types for the Java byte, short and char, int, long types respectively (with the exceptions stated for JCGO_INTFIT, JCGO_USELONG macros) /
/ Assume sizeof(int) is 4, so use C int (not long or __int32) for the Java int type /
/ Use C long for the Java long type (otherwise, use either C __int64 or long long type) /
/ Only if JCGO_USELONG is not defined: use "LL" suffix for __int64 type values or "i64" suffix for long long type values (vice versa, otherwise) /
/ Do not use C float and double types and floating-point arithmetics at all (in this case the Java float and double types are represented by the Java int and long types respectively) /
/ Only if JCGO_NOFP is not defined: use C long double type (to represent Java double type and perform all floating-point calculations with the extended precision) instead of the (normal) double type (note that JNI is affected too, so JCGO_LONGDBL should not be normally defined if JCGO_NOJNI is not defined) /
/ Only if JCGO_SEPARATED is not defined: do not mark Java functions as inline that are used before their definitions in the generated C code (no "forward" inlining) /
/ Do not use "const" keyword for immutable C struct members (fields) /
/ Prefix JNI functions names with additional "_" (underscore) /
/ Only if JCGO_THREADS and JCGO_WIN32 are defined: allow to switch the system timer to the highest possible resolution when needed /
/ Only if JCGO_THREADS is defined, and all of JCGO_WIN32, JCGO_OS2 and JCGO_SOLTHR are not defined: use PThread timed wait based on monotonic clock /
/ Only if JCGO_THREADS is defined, and JCGO_OS2 or JCGO_WIN32 is defined: use OS CreateThread() API call instead of C _beginthread() /
/ Allow to allocate and access "huge" arrays (occupying multiple adjacent memory segments); only for "large" data address models /
/ Only if JCGO_NOGC is not defined and JCGO_THREADS is defined: use (GC_get_parallel() + 1) value as the number of available CPUs /
/ Do not use memory garbage collector, use the standard calloc instead, so that the allocated memory is never reclaimed (and finalizers are never executed) /
/ Store and use the GCJ-style length-based type descriptors (useful only if JCGO_NOGC is not defined) to make garbage collection a bit more accurate /
/ Only if JCGO_NOGC is not defined: clear "static data roots" preset by the garbage collector at start-up and disable dynamic library data segments registering /
/ Only if JCGO_NOGC is not defined: do not turn off "all-interior-pointers" recognition mode of the garbage collector /
/ Only if JCGO_NOGC is not defined: force (explicitly turn on) GC incremental mode (should be used with great care unless JCGO_NOSEGV or JCGO_WIN32 is defined) /
/ Only if JCGO_NOGC is not defined: use shared version of GC library /
/ Only if JCGO_NOGC is not defined: use the debug version of GC malloc /
/ Only if JCGO_NOGC is not defined and JCGO_THREADS is defined: do not redirect C library thread creation calls to GC (use explicit GC thread registration instead) /
/ Only if JCGO_NOGC is not defined: force immediate memory unmapping (if supported) on explicitly-initiated garbage collections by default /
/ Only if JCGO_NOGC is not defined: set the desired initial heap size (in bytes) /
define GC_INITIAL_HEAP_SIZE 1024*1024
/ Only if JCGO_NOGC is not defined: explicitly specify GC_free_space_divisor value (otherwise, the default value is used) /
define GC_FREE_SPACE_DIVISOR 5
/ Only if JCGO_NOGC is not defined: explicitly specify calling convention for the GC API functions /
define GC_CALL __cdecl
/ Only if JCGO_NOGC is not defined: explicitly specify an alternate calling convention for the GC API user callbacks /
define GC_CALLBACK __cdecl
/ Do not use C "const" keyword /
define CONST /**/
/ Do not inline functions /
define INLINE /**/
/ Do not use C "static" keyword for functions (i.e., use external linkage for all functions) /
define STATIC /**/
/ Use internal linkage for some C functions that should normally have external linkage (visibility) /
define EXTRASTATIC static
/ Use "dllimport" declaration modifier for imported functions /
define JNIIMPORT __declspec(dllimport)
/ Use "dllexport" declaration modifier for exported functions /
define JNIEXPORT __declspec(dllexport)
/ Only if JCGO_NOJNI is not defined: explicitly use "dllexport" for Java VM Invocation API functions /
define JNIEXPORT_INVOKE __declspec(dllexport)
/ Use "static" declaration modifier for some (considerable) JNU functions (instead of JNIEXPORT modifier) /
define JNUBIGEXPORT static
/ Use "stdcall" calling convention for JNI library /
define JNICALL __stdcall
/ Only if JCGO_NOJNI is not defined: explicitly specify "stdcall" calling convention for Java VM Invocation API functions /
define JNICALL_INVOKE __stdcall
/ Do not use "fast calling" convention explicitly /
define CFASTCALL /**/
/ Do not use "cdecl" calling convention for C runtime library callbacks /
define CLIBDECL /**/
/ Do not perform explicit initialization of the floating-point module /
define FPINIT /**/
/ Only if JCGO_THREADS is defined: do not perform explicit initialization of the C threads library /
define THREADSINIT /**/
/ Only if JCGO_THREADS is defined: explicitly specify default stack size for non-main threads (zero for system-specific stack size) /
define THREADSTACKSZ 0
/ Only if JCGO_SEPARATED is not defined: do not use C "static" storage class for global variables (i.e., use external linkage for all global data) /
define STATICDATA /**/
/ Only if JCGO_SEPARATED is not defined: override C storage class (specified by STATICDATA) for global GC-sensitive variables (useful only if JCGO_NOGC is not defined) /
define GCSTATICDATA /**/
/ Only if JCGO_NOGC is not defined: explicitly instruct the garbage collector about the first GC-sensitive (i.e., which could hold pointers to heap-allocated Java objects) symbol placed to "data" section by the target code linker /
define GCDATAFIRSTSYM java_lang_String__class
/ Only if JCGO_NOGC is not defined: explicitly instruct the garbage collector about the last GC-sensitive symbol placed to "data" section by the target code linker /
define GCDATALASTSYM jcgo_noTypesClassArr
/ Only if JCGO_NOGC is not defined: explicitly instruct the garbage collector about the first GC-sensitive symbol placed to "bss" section by the target code linker /
define GCBSSFIRSTSYM jcgo_initialized
/ Only if JCGO_NOGC is not defined: explicitly instruct the garbage collector about the last GC-sensitive symbol placed to "bss" section by the target code linker /
define GCBSSLASTSYM jcgo_globData
/ Specify an alternate section to place all C global variables which are non-zero initially and, besides, could not hold pointers to any heap-allocated Java object during run time (useful only if JCGO_NOGC is not defined); it may be defined or undefined independently for every class if JCGO_SEPARATED is defined /
define ATTRIBNONGC attribute((section(".dataord")))
/ Specify an alternate section to place all C global non-zero variables which could hold pointers to heap-allocated Java objects (useful only if JCGO_NOGC is not defined and JCGO_GCRESETDLS is defined; should be used instead of ATTRIBNONGC when the target C compiler does not place the read-only data into a separate program section) /
define ATTRIBGCDATA attribute((section(".datagc")))
/ Specify an alternate section to place all C global variables which are initialized to zero and could hold pointers to heap-allocated Java objects (useful only if JCGO_NOGC is not defined and JCGO_GCRESETDLS is defined) /
define ATTRIBGCBSS attribute((section(".bss4gc")))
/ Ignore GNU C 'malloc' attribute (for some memory allocation internal functions) /
define ATTRIBMALLOC /**/
/ Ignore 'noreturn' attribute of the Java 'throw' statement /
define DECLSPECNORET /**/
/ Ignore branch probabilities specified via GNU C __builtin_expect /
define BUILTINEXPECTR /**/
/ Explicitly specify the decl and the name of C main entry function /
define MAINENTRY int//__cdecl//main
/ Prototype all "JNI_OnLoad" and "JNI_OnUnload" external functions (using JNIONLOAD and JNIONUNLOAD macros) those names are specified in either JNIONLOADLIST or JNIONUNLOADLIST lists /
define JNIONLOADDECLS JNIONLOAD(JNI_OnLoad1)JNIONUNLOAD(JNI_OnUnload1)
/ Specify comma-separated names list of "JNI_OnLoad" functions to call /
define JNIONLOADLIST JNI_OnLoad1,JNI_OnLoad2
/ Specify comma-separated names list of "JNI_OnUnload" functions to call /
define JNIONUNLOADLIST JNI_OnUnload1,JNI_OnUnload2
/ Link native package.Class.jniFunc() to a stub (aborting the execution) instead of linking it to the external Java_package_Class_jniFunc() /
/ Specify the default value for "JAVA_PROPS" environment variable (if the latter is unset); the string value opening quote must be prefixed with 'L' if and only if JCGO_WMAIN is defined /
define JAVADEFPROPS ""
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