extern volatile int x;
extern fff(int);
int f() {
fff(x=1);
return x=1;
}
#if 0
The code generated by gcc below from the source code above shows that the value
of the expression x=1, when x is volatile, depends on the context, most likely
violating the standard.
In a return statement, the value is 1. In an argument being passed to a
function, the value is the value obtained by fetching the contents of x after
the assignment is made.
The command used was
gcc -S -O2 -c bar.c
.file "bar.c"
.text
.p2align 4,,15
.globl f
.type f, @function
f:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
movl $1, x
movl x, %eax
movl %eax, (%esp)
call fff
movl $1, %eax
movl $1, x
leave
ret
.size f, .-f
.ident "GCC: (Ubuntu 4.3.2-1ubuntu11) 4.3.2"
.section .note.GNU-stack,"",@progbits
$ uname -a
Linux gallium 2.6.27-9-generic #1 SMP Thu Nov 20 21:57:00 UTC 2008 i686
GNU/Linux
$ cat /etc/issue
Ubuntu 8.10 \n \l
#endif
--
Summary: semantics of assignment in a return statement suspect
Product: gcc
Version: 4.3.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dan at math dot uiuc dot edu
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38679
