When passing the result of __builtin_bswap32() to printf() and -Wformat is enabled, the following code:
#include <stdio.h> int foo(unsigned int arg) { return printf("%u", __builtin_bswap32(arg)); } generates this odd diagnostic: foo.c:3: warning: format '%u' expects type 'unsigned int', but argument 2 has type 'unsigned int' Strangely enough, if I use "%d" instead of "%u", no diagnostic is generated. I haven't checked the details of __builtin_bswap32()'s implementation, but I wonder if this might be the same issue as (or related to) bug 21962? -- Summary: Bogus diagnostic: format '%u' expects type 'unsigned int', but argument 2 has type 'unsigned int' Product: gcc Version: 4.4.4 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: gcczilla1 at achurch dot org GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44502