Consider this code:
int foo(int a, unsigned b)
{
return a != b;
}
int bar(int a, unsigned b)
{
return (unsigned)a != b;
}
int foobar(int a, unsigned b)
{
return a != (int)b;
}
$ gcc -O2 -Wall -W foo.c -c
foo.c: In function foo:
foo.c:3: warning: comparison between signed and unsigned integer expressions
The generated code is identical for all 3 functions, so there is no reason
to "fix" the warning in the code. Rather I think gcc shouldn't warn in this
case at all.
A more realistic example:
#include <unistd.h>
int foo(int fd, char *buf, size_t n)
{
return (read(fd, buf, n) != n);
}
FWIW, if I change int to 'short int' or 'signed char' (and unsigned
appropriately) I get no warning.
--
Summary: 'warning: comparison between signed and unsigned'
shouldn't be given for equality comparisons
Product: gcc
Version: 4.3.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: edwintorok at gmail dot com
GCC build triplet: x86_64-linux-gnu
GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38046
