https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90472
Bug ID: 90472
Summary: “extern int i;” declaration inside function is allowed
to shadow “static int i;” at file scope
Product: gcc
Version: 9.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: pascal_cuoq at hotmail dot com
Target Milestone: ---
Consider the two compilation units below, that differ only in the name of the
automatic variable inside function f:
____
int *p1, *p2;
static int i = 1;
void f(void) {
p1 = &i;
int i = 2;
{
extern int i;
p2 = &i;
}
}
____
int *p1, *p2;
static int i = 1;
void f(void) {
p1 = &i;
int j = 2;
{
extern int i;
p2 = &i;
}
}
____
Using GCC 9.1, the first file is accepted and the “obvious” assembly code is
generated (the function f assigns the same value to p1 and p2). The second file
is rejected with the error message:
<source>: In function 'f':
<source>:9:20: error: variable previously declared 'static' redeclared 'extern'
9 | extern int i;
| ^
Compiler Explorer link: https://gcc.godbolt.org/z/wrvZ1d
I rather agree with the error message, and my understanding of C11 6.7:3
(https://port70.net/~nsz/c/c11/n1570.html#6.7p3 ) is that both compilation
units should be rejected. In any case, the two look equivalent, and they should
probably either be both accepted or both rejected.
(If you arrive to the conclusion that the C11 standard says they should both be
rejected, I will have a similar bug to report in Clang.)
