https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107274
Bug ID: 107274
Summary: Incorrect -Wuninitialized on indexed initialization
Product: gcc
Version: 12.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: keegan at undefinedbehaviour dot org
Target Milestone: ---
Given:
void
example(unsigned long val)
{
unsigned char b[4];
b[0] = val;
b[1] = val >> 8;
b[2] = val >> 16;
b[3] = val >> 24;
val = *(unsigned long *)b;
}
GCC 12.2 issues the following (incorrect) diagnostic:
issue.c: In function 'example':
issue.c:11:13: warning: 'b' is used uninitialized [-Wuninitialized]
11 | val = *(unsigned long *)b;
| ~~~~^~~~~~~~~~~~~~~~~~~~~
issue.c:4:23: note: 'b' declared here
4 | unsigned char b[4];
| ^
Instead this code is correct in that it initializes all fields of "b". It
appears the cast indirection is what is causing the issue, because I cannot get
the diagnostic to be issued for other uses.
