Re: Wrestling with exceptions on win32 gcj 4.1

[Adam Megacz <megacz at cs dot berkeley dot edu>]

I've been a bit out of the loop, but I believe you need
--enable-sjlj-exceptions on Win32... unless somebody added DWARF2
unwind support on that platform in the last year.

  - a


"tHE DPR" <dpr@aha.lt> writes:
> hello,
>
> i'm trying to build a win32 crosscompiler on linux.
> as i learned on this list already, exception support doesn't work very
> well on windows.
> but i tried...
>
> so, i was able to build a crosscompiler with these configure options:
>
> Target: i686-pc-mingw32
> Configured with: /home/dpr/gcc/gcc-4.1/configure
> --prefix=/home/dpr/gcc/crossgcc --target=i686-pc-mingw32
> --host=i686-pc-linux-gnu --build=i686-pc-linux-gnu
> --enable-languages=c,c++,java --disable-nls --enable-threads=win32
> --with-gcc --with-gnu-as --with-gnu-ld --without-newlib
> --disable-win32-registry --disable-shared --enable-libgcj
> --disable-java-awt --without-x --enable-java-gc=boehm
> --enable-interpreter --disable-debug --disable-libgcj-debug
> Thread model: win32
> gcc version 4.1.0 20060203 (prerelease)
>
> compiler builds, a hello world builds, but doesn't work
>
> as i figured out, the problem is that all libjava is built with
> -fomit-frame-pointer.
> i hacked configure.host file and changed -fomit-frame-pointer to
> -fno-omit-frame-pointer.
> now hellow world buils and runs ok.
>
> now second problem...
> it appears that it's impossible to load a jni library:
>
> my modified hellow world crashes because of segfault:
>
> public class Test
> {
>     public static void main(String[] args)
>     {
>         System.out.println("Hello, GCJ!");
>         try
>         {
>             new StringBuffer().append("123".toCharArray(), 1, 5);
>         }
>         catch (Exception ex)
>         {
>             ex.printStackTrace();
>         }
>         System.loadLibrary("any-lib");
>     }
> }
>
> (gdb) run
> Starting program: N:\gcc\test/Test.exe
> Hello, GCJ!
> java.lang.StringIndexOutOfBoundsException
>    at 0x548c48 (Unknown Source)
>    at 0x40580e (Unknown Source)
>    at 0x40a282 (Unknown Source)
>    at 0x40a5d3 (Unknown Source)
>    at 0x40a5ed (Unknown Source)
>    at 0x40a60d (Unknown Source)
>    at 0x40a6ad (Unknown Source)
>    at 0x40a6cd (Unknown Source)
>    at 0x4153aa (Unknown Source)
>    at 0x401471 (Unknown Source)
>    at 0x5af5cc (Unknown Source)
>    at 0x430497 (Unknown Source)
>    at 0x450b10 (Unknown Source)
>    at 0x4042f0 (Unknown Source)
>    at 0x404452 (Unknown Source)
>    at 0x404487 (Unknown Source)
>    at 0x401308 (Unknown Source)
>    at 0x401233 (Unknown Source)
>    at 0x401284 (Unknown Source)
>    at 0x7c816d4b (Unknown Source)
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00401679 in _Unwind_GetIP ()
>
> (gdb) backtrace
> #0  0x00401679 in _Unwind_GetIP ()
> #1  0x0040196d in _Unwind_Backtrace ()
> #2  0x0054f463 in _Jv_StackTrace::GetFirstNonSystemClassLoader ()
> #3  0x0042bb91 in java::lang::Runtime::_load ()
> #4  0x0040bb70 in java::lang::Runtime::loadLibrary ()
> #5  0x0040b37c in java::lang::System::loadLibrary ()
> #6  0x00401489 in dpr.Test.main(java.lang.String[]) (args=0xf76fb8)
>     at dpr/Test.java:16
> #7  0x005af5d0 in gnu::java::lang::MainThread::call_main ()
> #8  0x0043049b in gnu::java::lang::MainThread::run ()
> #9  0x00450b14 in _Jv_ThreadRun ()
> #10 0x004042f4 in _Jv_RunMain ()
> #11 0x00404456 in _Jv_RunMain ()
> #12 0x0040448b in JvRunMain ()
> #13 0x0040130c in main (argc=4199180, argv=0x731040) at /tmp/cc7J0XGe.i:11
>
> (gdb) disassemble
> Dump of assembler code for function _Unwind_GetIP:
> 0x00401670 <_Unwind_GetIP+0>:   push   %ebp
> 0x00401671 <_Unwind_GetIP+1>:   mov    %esp,%ebp
> 0x00401673 <_Unwind_GetIP+3>:   mov    0x8(%ebp),%eax
> 0x00401676 <_Unwind_GetIP+6>:   pop    %ebp
> 0x00401677 <_Unwind_GetIP+7>:   mov    (%eax),%eax
> 0x00401679 <_Unwind_GetIP+9>:   mov    0x4(%eax),%eax
> 0x0040167c <_Unwind_GetIP+12>:  inc    %eax
> 0x0040167d <_Unwind_GetIP+13>:  ret
> 0x0040167e <_Unwind_GetIP+14>:  mov    %esi,%esi
> End of assembler dump.
>
> i traced the problem down to the method
> _Jv_StackTrace::UnwindTraceFn (btw, why it is not shown in backtrace?)
>
> it appears that this callback method is handed a context where
> context->fc == 0,
> and this happens after the last frame is processed with this data
>   context->fc->prev      ==  0
>   context->fc->call_site == -1
>
> i hope this makes sense to you.
>
> as i understand this, either UnwindTraceFn (or _Unwind_GetIP) should
> be prepared for this,
> or _Unwind_Backtrace should not call a callback with such context.
>
> btw, as i debugged all this, i noticed that UnwindTraceFn may return
> _URC_NORMAL_STOP (throught non_system_trace_fn), which is interpretted
> as _URC_FATAL_PHASE1_ERROR in _Unwind_Backtrace.
>
> in the end i hope this is a simple to fix problem, or just my mistake..
>
> bye,
> dpr
>
>

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