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From: "mikpe at it dot uu dot se" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug other/41809] New: escaping address of packed field should trigger warning Date: Fri, 23 Oct 2009 16:06:00 -0000 [thread overview] Message-ID: <bug-41809-7665@http.gcc.gnu.org/bugzilla/> (raw) A field in a packed struct will often not have the normal alignment for its type. So taking the address of such a field may yield a misaligned pointer, but gcc does not warn about that. This is similar to casting a pointer from a less aligned type to a more aligned type, which does give a warning (with -Wcast-align). Example: > cat aopf.c #include <stdio.h> void __attribute__((noinline)) f(int *p) { printf("%p\n", p); } struct s { int x; char c; } __attribute__((__packed__)); struct s A[10]; int main(void) { unsigned int i; for (i = 0; i < sizeof(A)/sizeof(A[0]); ++i) { f(&A[i].x); f((int*)(char*)&A[i].x); } return 0; } > gcc -Wall -Wextra -Wcast-align -O aopf.c aopf.c: In function 'main': aopf.c:21:4: warning: cast increases required alignment of target type Ideally both calls to f() should trigger alignment warnings. -- Summary: escaping address of packed field should trigger warning Product: gcc Version: 4.5.0 Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: other AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: mikpe at it dot uu dot se http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41809
next reply other threads:[~2009-10-23 16:06 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-10-23 16:06 mikpe at it dot uu dot se [this message] 2009-10-26 21:47 ` [Bug other/41809] " hp at gcc dot gnu dot org
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