Hello Jonathan,
[ Please CC me on sparse-llvm related issues. ]
On Thu, Jul 19, 2012 at 4:17 PM, Jonathan Neuschäfer
<j.neuschaefer@xxxxxxx> wrote:
> compiling a little real-world program with sparse-llvm, it segfaulted.
> Using a tool called "delta"[1] and some bash scripting, I managed to
> reduce the code to this test case:
>
> //struct foo {int a;};
> //struct foo;
> extern struct foo *foop;
> extern void func(struct foo *f);
> int main(int argc, char **argv) {
> func(foop);
> }
>
> (Uncommenting the commented lines doesn't change the crashing)
>
> gdb gives me this backtrace:
>
> (gdb) bt
> #0 0x080b86c1 in LLVMBuildPtrToInt ()
> #1 0x080530fd in output_op_load (insn=0xb742512c, fn=0xbf85624c) at sparse-llvm.c:595
> #2 output_insn (insn=0xb742512c, fn=0xbf85624c) at sparse-llvm.c:1008
> #3 output_bb (generation=7, fn=0xbf85624c, bb=<optimized out>) at sparse-llvm.c:1096
> #4 output_fn (module=0xb7738f0c, module@entry=0x8ccc750, ep=<error reading variable: Unhandled dwarf expression opcode 0xfa>,
> ep=<error reading variable: Unhandled dwarf expression opcode 0xfa>) at sparse-llvm.c:1166
> #5 0x080507ec in compile (list=0xb773858c, module=0x8ccc750) at sparse-llvm.c:1227
> #6 main (argc=2, argv=0xbf856684) at sparse-llvm.c:1246
>
> I'm using llvm version 3.0 (package version 1:3.0-14) from Debian and
> sparse v0.4.4-100-g063236f (the most recent commit in git).
The SIGSEGV is caused by pseudo_to_value() returning NULL for "foop".
AFAICT, we should use LLVMGetNamedGlobal() to look it up but
unfortunately output_data() is *not* called for "foop" at all so the
backend doesn't know about it.
Linus, Jeff, how does the sparse frontend deal with externs? Why isn't
"foop" visible after linearize_symbol()?
Pekka
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