Although I demonstrated this using 4.1.2 on my host, it probably affects other versions as well.
As the following code shows: gcc -c -O1 -Wall -Werror uninitialized-warning.c extern void called_function(unsigned p); extern unsigned g; void f0(unsigned parm) { unsigned v; if (parm == 0) { v = 4; } called_function(v); } void f1(unsigned parm) { unsigned v; if (parm == 0) { v = 4; } else { g = 0; } called_function(v); } void f2(unsigned parm) { unsigned v; called_function(v); } gcc does not produce the 'uninitialized' warning when the automatic variable is conditionally assigned. This gives a very bad false sense of security that the automatic variables are indeed initialized. -- Summary: -Wunintialized fails in the face of conditional assignment. Product: gcc Version: 4.1.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: thutt at vmware dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37148