Re: [Tinycc-devel] standalone backtraces

[Herman ten Brugge]

On 2020-01-19 02:01, grischka wrote:
> Herman ten Brugge via Tinycc-devel wrote:
> > Thanks for doing this. This was indeed needed.
> >
> > There are 2 problems I see.
> >
> > The first one is that you removed the alloca/vla code for bounds 
> > checking.
> > The following program:
> >
> > extern void *alloca(int size);
> > void tst1(void) { void *a = alloca(16); }
> > void tst2(void) { int i; int a[10]; for (i=0;i<10;i++)a[i]=0; }
> >
> > int main(void) { tst1(); tst2(); }
> >
> > When compiled with bounds checking it fails. The alloca
> > is not deleted because no __bound_local_delete is generated.
> > The original code in tccgen.c created a dummy lbounds section
> > so that __bound_local_new(not needed) and __bound_local_delete
> > were generated.
>
> How many dummy entries do you need to make sure __bound_local_delete
> is called, and do you need any at all, really?
I need only 1. I modified the code. See attached patch.
This solves both problems.
There is no alloca_free() so I need a trigger to remove the alloca/vla data.
> > The other problem is that testcase 112 produces on linux:
> > # ./tcc -b -dt 112_backtrace.c -o 112_backtrace -Dtest_bcheck_100
> > # ./112_backtrace
> > 112_backtrace.c:107: at main: BCHECK: 0x7ffed562f6e4 is outside of the
> > region
> > 112_backtrace.c:107: at main: BCHECK: invalid pointer 0x7ffed562f6da,
> > size 0xa in memcpy dest
> >
> > This looks correct.
> >
> > But on windows (and wine) I get:
> > # ./tcc.exe -b -dt 112_backtrace.c -o 112_backtrace.exe 
> > -Dtest_bcheck_100
> > # ./112_backtrace.exe
> > 00401535 : at ???: BCHECK: 000000000022FA84 is outside of the region
> > 00404447 : by ???
> > 00404666 : by ???
> > 112_backtrace.c:107: by main
> > 0040447a : at ???: BCHECK: invalid pointer 000000000022FA7A, size 0xa in
> > memcpy dest
> > 00404666 : by ???
> > 112_backtrace.c:107: by main
>
> That looks like missing -g when bcheck.c was compiled.
Oops. Need more coffee.
Fixed the Makefile.
> Btw, there seems to be a bug in the sym-version code that crashes
> tcc when it tries to link with a .so, for example:
>
>     echo "void f() {}" | tcc - -shared -o a.so
>     echo "main() {}" | tcc - a.so
>     <segmentation fault>
I cannot reproduce this. I checkout a fresh copy and see no problem.
I use Fedora 31 with all updates.

Regards,

    Herman

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