Hi René,

On Fri, 10 Feb 2017, René Scharfe wrote:

Am 10.02.2017 um 15:20 schrieb Johannes Schindelin:

quoted

It is curious that only MacOSX builds trigger an error about this, both
GCC and Clang, but not Linux GCC nor Clang (see
https://travis-ci.org/git/git/jobs/200182819#L1152 for details):

builtin/bisect--helper.c:299:6: error: variable 'good_syn' is used
  uninitialized whenever 'if' condition is true
  [-Werror,-Wsometimes-uninitialized]
        if (missing_good && !missing_bad && current_term &&
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
builtin/bisect--helper.c:350:7: note: uninitialized use occurs here
        if (!good_syn)
             ^~~~~~~~

The only way that good_syn could be used in the if block is by going to the
label finish, which does the following before returning:

	if (!bad_ref)
		free(bad_ref);
	if (!good_glob)
		free(good_glob);
	if (!bad_syn)
		free(bad_syn);
	if (!good_syn)
		free(good_syn);

On Linux that code is elided completely -- freeing NULL is a no-op.  I guess
free(3) has different attributes on OS X and compilers don't dare to optimize
it away there.

So instead of calling free(3) only in the case when we did not allocate memory
(which makes no sense and leaks) we should either call it in the opposite
case, or (preferred) unconditionally, as it can handle the NULL case itself.
Once that's fixed initialization will be required even on Linux.

Exactly, free(NULL) is a no-op. The problem before this fixup was that
good_syn was not initialized to NULL.

Ciao,
Dscho