Frontend issue on conditional operator in C

[skcho]

int foo ()
{
  int x = ({1 ? 1 : 1;});
  return 0;
}

Current front-end parses the above example into an incorrect control flow graph, where return node is unreachable from the entry node. This issue was initially observed when compiling strspn() with gcc -O2 and clang -O2 as follows.

#include <string.h>

int foo (char *s)
{
  size_t n_slash = strspn (s, "/");
  return 0;
}

[akotulski]

Thanks for reporting - we did take some shortcuts translating statement expressions and if you pair it with conditional operators it may end up here.

On the other hand, how did you make source of strspnavailable for infer? Usually we use models for C library

[skcho]

Thank you for the reply. We just downloaded gnu gzip 1.8 and run

./configure
infer -a checkers -- make

The default setting of the Makefile uses the -O2 option, and then strspn is inlined.

[akotulski]

I looked more into the issue and found the problem: clang AST is looking differently when compiled with -O2 and we don't want that. Infer has a model for strspn which we should use.
I'm going to fix issue with -O2 and I'll leave "conditional inside statement expression" problem

[skcho]

Thanks. It works now in our case.

[akotulski]

I just tested the repro case and it works now, probably because of e366b0d