From: mickish@cmu.edu (Andrew Mickish) Subject: Java JNI with GNU-WIN32 gcc 22 Sep 1998 07:59:14 -0700 Message-ID: <360650CC.5EAB82C8.cygnus.gnu-win32@cmu.edu> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------34D05A37FC18318E3F94F764" To: gnu-win32@cygnus.com, teh@ic.eecs.berkeley.edu This is a multi-part message in MIME format. --------------34D05A37FC18318E3F94F764 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit FAQ Maintainers: Please add this info to your sites. _________________________________________________________________ Subject: More Java JNI with GNU-WIN32 gcc Date: Tue, 30 Jun 1998 14:05:03 -0400 From: Andrew Mickish To: gnu-win32@cygnus.com Here are a few more issues that came up when trying to compile a JNI DLL with gcc. * There are two different problems that could cause Unsatisfied link errors. One is if the DLL is not found, and the other is if the DLL is found but is unreadable or the specific function cannot be found in it. These problems are distinguishable by the stack trace that you get below the "Unsatisfied link error," and also by testing for changes in behavior when you run Java after deliberately deleting the DLL or deliberately renaming some arbitrary text file to be your DLL. * The directory containing the DLL ought to be in your PATH. The recommended way to set your path is to change it with the System control panel and open a new window. The cygnus.bat file munges the path a little itself, so my own path ends up looking like this: bash-2.01$ echo $PATH /Cygnus/B19/H-i386-cygwin32/bin:/WINNT/system32:/WINNT:/utils:/enscript://E/jdk1.1.5/bin://E/java/HelloWorld * I had to hand-edit the DEF file and put in an alias for the exported function. Without the alias, it seems that Cygnus is exporting the mangled name of the function with its offset ("...@8") and Java is looking for an unmangled name. My DEF file looks like this: bash-2.01$ cat hello.def EXPORTS Java_HelloWorld_displayHelloWorld=Java_HelloWorld_displayHelloWorld@8dll_entry@12 Please let me know if any of this has been helpful. --Andrew Mickish mickish@cmu.edu __________________________________________________________________ Subject: Java JNI with GNU-WIN32 gcc Date: Thu, 11 Jun 1998 19:48:11 -0400 From: Andrew Mickish To: gnu-win32@cygnus.com > With significant help from Bill Pringlemeir, I figured out how to > compile Sun's JNI tutorial HelloWorld example under GNU-WIN32 with > gcc. I will keep a ZIP file of the gcc-compatible code at > http://www.andrew.cmu.edu/~am2q/HelloWorld.zip for future reference. > > Please add this information to the GNU-WIN32 documentation and FAQ. > As of version 19.1, it is significantly more complicated to compile > a Java-compatible DLL under gcc than under Microsoft Visual C++. > Even printf() does not work in a gcc-compiled DLL, even thoough it > works fine with VC++. Will this be changing with future releases > of GNU-WIN32? > > Here are a few hints for how to compile a trivial JNI-compaible DLL > with gcc: > > 1) You need init.cc, an element of building relocatable DLLs > > 2) There is a complicated linking procedure involving ld and > intermediate files: > > ld --base-file hello.base --dll -o hello.dll HelloWorldImp.o > init.o $(LIB) -e _dll_entry@12 > dlltool --as=as --dllname hello.dll --def hello.def > --base-file hello.base --output-exp hello.exp > ld --base-file hello.base hello.exp --dll -o hello.dll > HelloWorldImp.o init.o $(LIB) -e _dll_entry@12 > dlltool --as=as --dllname hello.dll --def hello.def --base-file > hello.base --output-exp hello.exp > ld hello.exp --dll -o hello.dll HelloWorldImp.o init.o $(LIB) > -e _dll_entry@12 > > 3) Printf will not work here. Use a Windows dialog box or > call back into Java to invoke System.out.println(): > > void jprintf (JNIEnv *env, char* str) { > > jstring jstr = (*env)->NewStringUTF(env, str); > jclass System_class = (*env)->FindClass(env, > "java/lang/System"); > jfieldID fid_out = (*env)->GetStaticFieldID( > env, System_class, "out", > "Ljava/io/PrintStream;"); > jobject out = (*env)->GetStaticObjectField( > env, System_class, fid_out); > jclass PrintStream_class = (*env)->FindClass(env, > "java/io/PrintStream"); > jmethodID mid_println = (*env)->GetMethodID(env, > PrintStream_class, > "println", > (Ljava/lang/String;)V"); > if (mid_println == 0) { > exit(1); > } > (*env)->CallVoidMethod(env, out, mid_println, jstr); > } > > > JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld( > JNIEnv *env, jobject obj) > { > (void)env; (void)obj; > MessageBoxA(NULL,"Hello Jupiter!", "Hello world!", 0); > jprintf(env, "Hello Uranus!\n"); > return; > } > > > A collection of files that implement Sun's JNI HelloWorld example > may be found at http://www.andrew.cmu.edu/~am2q/HelloWorld.zip > > --Andrew Mickish > mickish@cmu.edu > --------------34D05A37FC18318E3F94F764 Content-Type: message/rfc822; name="nsmailG1.TMP" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="nsmailG1.TMP" Return-Path: Received: from po2.andrew.cmu.edu (PO2.ANDREW.CMU.EDU [128.2.10.102]) by mail1.andrew.cmu.edu (8.8.5/8.8.2) with ESMTP id GAA25864 for ; Fri, 12 Jun 1998 06:45:42 -0400 (EDT) Received: (from daemon@localhost) by po2.andrew.cmu.edu (8.8.5/8.8.2) id GAA01192 for am2q+@MAIL1.ANDREW.CMU.EDU; Fri, 12 Jun 1998 06:37:08 -0400 (EDT) Received: via switchmail for am2q+@andrew.cmu.edu; Fri, 12 Jun 1998 06:37:08 -0400 (EDT) Received: from cmu2.cs.cmu.edu (CMU2.CS.CMU.EDU [128.2.206.46]) by po2.andrew.cmu.edu (8.8.5/8.8.2) with ESMTP id GAA01187; Fri, 12 Jun 1998 06:37:06 -0400 (EDT) Received: (from daemon@localhost) by cmu2.cs.cmu.edu (8.8.5/8.8.5) id GAA21111; Fri, 12 Jun 1998 06:37:05 -0400 (EDT) Received: via localmail; Fri, 12 Jun 1998 06:37:04 -0400 (EDT) Received: from cygnus.com (runyon.cygnus.com [205.180.230.5]) by cmu2.cs.cmu.edu (8.8.5/8.8.5) with ESMTP id GAA21107; Fri, 12 Jun 1998 06:37:03 -0400 (EDT) Received: (from majordom@localhost) by runyon.cygnus.com (8.8.7-cygnus/8.8.7) id QAA28662; Thu, 11 Jun 1998 16:49:00 -0700 (PDT) Received: from mail6.bellatlantic.net (mail6.bellatlantic.net [151.201.0.38]) by runyon.cygnus.com (8.8.7-cygnus/8.8.7) with ESMTP id QAA28648 for ; Thu, 11 Jun 1998 16:48:57 -0700 (PDT) Received: from cmu.edu (client201-118-4.bellatlantic.net [151.201.118.4]) by mail6.bellatlantic.net (8.8.5/8.8.5) with ESMTP id SAA26371 for ; Thu, 11 Jun 1998 18:48:51 -0500 (EST) Message-ID: <35806CBB.7ACABDDD@cmu.edu> Date: Thu, 11 Jun 1998 19:48:11 -0400 From: Andrew Mickish X-Mailer: Mozilla 4.04 [en] (WinNT; U) MIME-Version: 1.0 To: gnu-win32@cygnus.com Subject: Java JNI with GNU-WIN32 gcc Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-gnu-win32@cygnus.com Precedence: bulk With significant help from Bill Pringlemeir, I figured out how to compile Sun's JNI tutorial HelloWorld example under GNU-WIN32 with gcc. I will keep a ZIP file of the gcc-compatible code at http://www.andrew.cmu.edu/~am2q/HelloWorld.zip for future reference. Please add this information to the GNU-WIN32 documentation and FAQ. As of version 19.1, it is significantly more complicated to compile a Java-compatible DLL under gcc than under Microsoft Visual C++. Even printf() does not work in a gcc-compiled DLL, even thoough it works fine with VC++. Will this be changing with future releases of GNU-WIN32? Here are a few hints for how to compile a trivial JNI-compaible DLL with gcc: 1) You need init.cc, an element of building relocatable DLLs 2) There is a complicated linking procedure involving ld and intermediate files: ld --base-file hello.base --dll -o hello.dll HelloWorldImp.o init.o $(LIB) -e _dll_entry@12 dlltool --as=as --dllname hello.dll --def hello.def --base-file hello.base --output-exp hello.exp ld --base-file hello.base hello.exp --dll -o hello.dll HelloWorldImp.o init.o $(LIB) -e _dll_entry@12 dlltool --as=as --dllname hello.dll --def hello.def --base-file hello.base --output-exp hello.exp ld hello.exp --dll -o hello.dll HelloWorldImp.o init.o $(LIB) -e _dll_entry@12 3) Printf will not work here. Use a Windows dialog box or call back into Java to invoke System.out.println(): void jprintf (JNIEnv *env, char* str) { jstring jstr = (*env)->NewStringUTF(env, str); jclass System_class = (*env)->FindClass(env, "java/lang/System"); jfieldID fid_out = (*env)->GetStaticFieldID(env, System_class, "out", "Ljava/io/PrintStream;"); jobject out = (*env)->GetStaticObjectField(env, System_class, fid_out); jclass PrintStream_class = (*env)->FindClass(env, "java/io/PrintStream"); jmethodID mid_println = (*env)->GetMethodID(env, PrintStream_class, "println", "(Ljava/lang/String;)V"); if (mid_println == 0) { exit(1); } (*env)->CallVoidMethod(env, out, mid_println, jstr); } JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject obj) { (void)env; (void)obj; MessageBoxA(NULL,"Hello Jupiter!", "Hello world!", 0); jprintf(env, "Hello Uranus!\n"); return; } A collection of files that implement Sun's JNI HelloWorld example may be found at http://www.andrew.cmu.edu/~am2q/HelloWorld.zip --Andrew Mickish mickish@cmu.edu - For help on using this list (especially unsubscribing), send a message to "gnu-win32-request@cygnus.com" with one line of text: "help". --------------34D05A37FC18318E3F94F764-- - For help on using this list (especially unsubscribing), send a message to "gnu-win32-request@cygnus.com" with one line of text: "help".