[fpc-pascal] LLVM crash

[Benito van der Zander]

Hi
> On which platform? When I compile the attached tt.pp file with -gw4 
> -Clfsanitize=address (LLVM 13, Debian 11, x86-64) and then run it, I 
> get the output in tt.txt. It includes line information.
>
> You could try lldb instead of gdb, although gdb should also be able to 
> handle debug information generated by LLVM. 

Ubuntu 22.04, LLVM 13

Nothing helps.


only some units are affected

Actually, now I see the warnings during compilation

Assembling xquery
mismatched subprogram between llvm.dbg.addr variable and !dbg attachment
inlinable function call in a function with debug info must have a !dbg 
location
   invoke void 
@"\01XQUERY$_$IXQVALUE_$__$$_$finalize$IXQVALUE"(%typ.XQUERY.IXQValue* 
%reg.1_200)
           to label %.Lj9768 unwind label %.Lj9743
.....
  call void @llvm.dbg.addr(metadata %typ.SYSTEM.TRTLCriticalSection* 
%tmp.1, metadata !48637, metadata !DIExpression()), !dbg !48773
label %0
void ()* @"\01XQUERY_$$_finalize$"
!48637 = !DILocalVariable(name: "_zero_$SYSTEM_$$_TRTLCRITICALSECTION", 
scope: !48635, file: !3, line: 10567, type: !1260)
!48635 = distinct !DISubprogram(name: "XQUERY_$$_init$", scope: !3, 
file: !3, line: 3506, type: !7606, scopeLine: 10504, spFlags: 
DISPFlagDefinition, unit: !2)
!48773 = !DILocation(line: 10570, column: 1, scope: !48772)
!48772 = distinct !DISubprogram(name: "XQUERY_$$_finalize$", scope: !3, 
file: !3, line: 10570, type: !7606, scopeLine: 10570, spFlags: 
DISPFlagDefinition, unit: !2)
warning: ignoring invalid debug info in 
/home/theo/lib/fpc/x86_64-linux/xquery.ll



The first appears to be caused by my managed operator patch

Then there is the default issue 
https://gitlab.com/freepascal.org/fpc/source/-/issues/40395
(and you have fixed it while I was still writing this mail)

Then this:

https://gitlab.com/freepascal.org/fpc/source/-/issues/40280 is causing a 
stack corruption

https://gitlab.com/freepascal.org/fpc/source/-/issues/40392 is causing a 
heap corruption


Cheers,
Benito
On 11.08.23 12:57, Jonas Maebe via fpc-pascal wrote:
> On 10/08/2023 23:27, Benito van der Zander via fpc-pascal wrote:
>> i tried to run my program under LLVM (from july fpc)  and it crashes?
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x000000000042e5f1in SYSTEM_$$_SYSGETMEM_FIXED$QWORD$$POINTER()
>> (gdb) bt
>> #0 0x000000000042e5f1in SYSTEM_$$_SYSGETMEM_FIXED$QWORD$$POINTER()
>> #1 0x000000000041b92ain fpc_ansistr_setlength()
>> #2 0x0000000000558d52in RESETBUFFER(ABUFFER=0x7fffffffd560, 
>> BASECAPACITY=130) at bbutils.pas:1650
>> #3 INIT(ABUFFER=0x7fffffffd560, BASECAPACITY=130, AENCODING=65001) at 
>> bbutils.pas:1639
>> #4 STRDECODEHTMLENTITIES(result=0x0, P=<optimized out>, L=130, 
>> ENCODING=65001, FLAGS=...) at bbutils.pas:5527
>>
>> anyone has seen sysgetmem crash before?
>
> It suggests heap corruption.
>
>> Perhaps that is exactly the kind of things ASAN was supposed to detect.
>
> Possibly, yes.
>
>> But with ASAN, I get an error somewhere entirely else. And I do not 
>> understand it, because the function is shown as ~ 5000 lines of 
>> assembly.
>>
>> How can I see the mixed code with disassemble /rm in gdb? I tried to 
>> call fpc -gl, -gs and -gw, and nothing helps
>
> On which platform? When I compile the attached tt.pp file with -gw4 
> -Clfsanitize=address (LLVM 13, Debian 11, x86-64) and then run it, I 
> get the output in tt.txt. It includes line information.
>
> You could try lldb instead of gdb, although gdb should also be able to 
> handle debug information generated by LLVM.
>
>> And there are a lot of weird ASAN calls for trivial movs. Like:
>>
>> 0x00000000006f577c<+22204>: 48 8b bb c8 00 00 00 
>> movrdi,QWORDPTR[rbx+0xc8]
>> 0x00000000006f5783<+22211>: e8 18 cc d0 ff 
>> call0x4023a0<__asan_report_load8 at plt>
>> 0x00000000006f5788<+22216>: e8 13 cc d0 ff 
>> call0x4023a0<__asan_report_load8 at plt>
>> 0x00000000006f578d<+22221>: e8 0e cc d0 ff 
>> call0x4023a0<__asan_report_load8 at plt>
>> 0x00000000006f5792<+22226>: e8 09 cc d0 ff 
>> call0x4023a0<__asan_report_load8 at plt>
>> 0x00000000006f5797<+22231>: 48 89 c7 movrdi,rax
>> 0x00000000006f579a<+22234>: e8 01 cc d0 ff 
>> call0x4023a0<__asan_report_load8 at plt>
>> 0x00000000006f579f<+22239>: 48 89 cf movrdi,rcx
>> 0x00000000006f57a2<+22242>: e8 09 ca d0 ff 
>> call0x4021b0<__asan_report_store8 at plt>
>>
>> Are they supposed to be there?
>
> These are generated by LLVM's own code generator, so yes.
>
>
> Jonas
>
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