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From: "zia at aracnet dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/34001] New: Incorrect __attribute__ fastcall behavior Date: Mon, 05 Nov 2007 23:40:00 -0000 [thread overview] Message-ID: <bug-34001-15308@http.gcc.gnu.org/bugzilla/> (raw) 4byte structures that are passed as parameters to a fastcall routine will get passed as registers. This does not match the original fastcall convention, which passes such structures on the stack. Compiling this code: #include <stdio.h> typedef struct { int a; } my_struct; int __attribute__((fastcall)) foo(my_struct s, int b) { return s.a + b; } main() { my_struct ss; ss.a = 1; printf("\nfoo = %d.\n",foo(ss,2)); } Results in: . . movl $1, -12(%ebp) movl -12(%ebp), %ecx movl $2, %edx call _foo . . and . . .globl _foo _foo: pushl %ebp movl %esp, %ebp subl $24, %esp movl %ecx, -12(%ebp) movl %edx, -16(%ebp) movl -12(%ebp), %eax addl -16(%ebp), %eax leave ret With GCC. Using other compilers that support fastcall will pass the struct value on the stack. -- Summary: Incorrect __attribute__ fastcall behavior Product: gcc Version: 4.0.1 Status: UNCONFIRMED Severity: major Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: zia at aracnet dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34001
next reply other threads:[~2007-11-05 23:40 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-11-05 23:40 zia at aracnet dot com [this message] 2007-11-05 23:58 ` [Bug target/34001] " pinskia at gcc dot gnu dot org 2007-11-08 17:12 ` hjl at lucon dot org 2007-11-09 16:55 ` hjl at lucon dot org 2007-11-09 17:34 ` hjl at lucon dot org 2007-11-12 3:27 ` [Bug target/34001] Incorrect x86 " hjl at lucon dot org 2007-11-16 4:52 ` hjl at lucon dot org 2007-11-26 23:19 ` hjl at lucon dot org 2007-11-27 2:36 ` hjl at lucon dot org 2007-11-28 1:20 ` hjl at gcc dot gnu dot org 2007-11-28 1:25 ` hjl at lucon dot org
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