It looks like you can’t – see this bug report. (And this one, which is marked as a dupe of that one – it has an identical test case to yours.) Since it looks like the root-cause bug is almost 10 years old, it would seem it’s not an easy problem to solve. In fact, the second bug I linked to has the phrase “Never going to be fixed” in the discussion, so that doesn’t look good.
If it’s really important to you, clang does catch this one with -Wsometimes-uninitialized
, which is included with -Wall
:
a.c:3:7: warning: variable 'a' is used uninitialized whenever 'if' condition is
false [-Wsometimes-uninitialized]
if (b)
^
a.c:5:10: note: uninitialized use occurs here
return a;
^
a.c:3:3: note: remove the 'if' if its condition is always true
if (b)
^~~~~~
a.c:2:8: note: initialize the variable 'a' to silence this warning
int a;
^
= 0
1 warning generated.