http://llvm.org/bugs/show_bug.cgi?id=18046
Bug ID: 18046
Summary: uninitialized warning refers to practically irrelevant
code
Product: clang
Version: trunk
Hardware: PC
OS: FreeBSD
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
1. Source code (x.c):
int main(void)
{
for(const char *p = ""; p; ) { }
for(const char *q; (q = q + 1); ) { }
}
2. Command line:
clang -Wall x.c
3. Output:
x.c:3:26: warning: variable 'q' is used uninitialized whenever 'for' loop exits
because its condition is false [-Wsometimes-uninitialized]
for(const char *p = ""; p; ) { }
^
x.c:4:26: note: uninitialized use occurs here
for(const char *q; (q = q + 1); ) { }
^
x.c:3:26: note: remove the condition if it is always true
for(const char *p = ""; p; ) { }
^
x.c:4:19: note: initialize the variable 'q' to silence this warning
for(const char *q; (q = q + 1); ) { }
^
= 0
1 warning generated.
4. Notes:
a) Using ``++q'' instead of ``(q = q + 1)'' causes the reference to the
other loop to go away (the uninitialized warning for ``q'' is still given).
b) If ``q'' is instead created and used (without initialization) in a
non-loop block (eg., ``{ const char *q; (q = q + 1); }''), then the reference
also goes away.
c) Changing the condition of the 1st loop to ``1'' (always true) causes the
said warnings to go away.
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