https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113776
Bug ID: 113776
Summary: [14 regression] postgresql-16.1 build failure with
-Werror=vla in configure test
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: sjames at gcc dot gnu.org
CC: jsm28 at gcc dot gnu.org
Target Milestone: ---
I'm not sure if this is an issue in the configure test that postgres is using.
If so, I'll report it over there or to autoconf as appropriate.
(I think pg is doing something wrong here anyway as it's using CFLAGS it tests
for itself for all of its configure tests.)
Anyway, I originally reported this downstream in Gentoo at
https://bugs.gentoo.org/923804.
pg fails to build like:
```
pg_collation.c:46:1: error: conflicting types for ‘CollationCreate’; have
‘Oid(const char *, Oid, Oid, char, _Bool, int32, const char *, const char
*, const char *, const char *, const char *, _Bool, _Bool)’ {aka ‘unsigned
int(const char *, unsigned int, unsigned int, char, _Bool, int, const char
*, const char *, const char *, const char *, const char *, _Bool, _Bool)’}
46 | CollationCreate(const char *collname, Oid collnamespace,
| ^~~~~~~~~~~~~~~
In file included from pg_collation.c:25:
../../../src/include/catalog/pg_collation.h:88:17: note: previous declaration
of ‘CollationCreate’ with type ‘Oid(const char *, Oid, Oid, char, bool,
int32, const char *, const char *, const char *, const char *, const char *,
bool, bool)’ {aka ‘unsigned int(const char *, unsigned int, unsigned int,
char, unsigned char, int, const char *, const char *, const char *, const
char *, const char *, unsigned char, unsigned char)’}
88 | extern Oid CollationCreate(const char *collname, Oid
collnamespace,
| ^~~~~~~~~~~~~~~
pg_collation.c: In function ‘CollationCreate’:
pg_collation.c:207:48: error: passing argument 3 of ‘heap_form_tuple’ from
incompatible pointer type [-Wincompatible-pointer-types]
207 | tup = heap_form_tuple(tupDesc, values, nulls);
| ^~~~~
| |
| _Bool *
In file included from pg_collation.c:18:
../../../src/include/access/htup_details.h:715:87: note: expected ‘bool *’ {aka
‘unsigned char *’} but argument is of type ‘_Bool *’
715 | Datum
*values, bool *isnull);
```
This turns out to be because of a configure test getting confused:
```
#include <stdbool.h>
#ifndef bool
"error: bool is not defined"
#endif
#ifndef false
"error: false is not defined"
#endif
#if false
"error: false is not 0"
#endif
#ifndef true
"error: true is not defined"
#endif
#if true != 1
"error: true is not 1"
#endif
#ifndef __bool_true_false_are_defined
"error: __bool_true_false_are_defined is not defined"
#endif
struct s {
_Bool s : 1;
_Bool t;
} s;
char a[true == 1 ? 1 : -1];
char b[false == 0 ? 1 : -1];
char c[__bool_true_false_are_defined == 1 ? 1 : -1];
char d[(bool)0.5 == true ? 1 : -1];
/* See body of main program for 'e'. */
char f[(_Bool)0.0 == false ? 1 : -1];
char g[true];
char h[sizeof(_Bool)];
char i[sizeof s.t];
enum { j = false, k = true, l = false * true, m = true * 256 };
/* The following fails for
HP aC++/ANSI C B3910B A.05.55 [Dec 04 2003]. */
_Bool n[m];
char o[sizeof n == m * sizeof n[0] ? 1 : -1];
char p[-1 - (_Bool)0 < 0 && -1 - (bool)0 < 0 ? 1 : -1];
/* Catch a bug in an HP-UX C compiler. See
http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
*/
_Bool q = true;
_Bool *pq = &q;
int main() {
bool e = &s;
*pq |= q;
*pq |= !q;
/* Refer to every declared value, to avoid compiler optimizations. */
return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !!j + !k + !!l + !m +
!n + !o + !p + !q + !pq);
return 0;
}
```
With -O2 -Werror=vla, it recently started emitting:
```
<source>:30:1: warning: variably modified 'd' at file scope
30 | char d[(bool)0.5 == true ? 1 : -1];
| ^~~~
<source>:30:1: error: ISO C90 forbids array 'd' whose size cannot be evaluated
[-Werror=vla]
<source>:32:1: warning: variably modified 'f' at file scope
32 | char f[(_Bool)0.0 == false ? 1 : -1];
| ^~~~
<source>:32:1: error: ISO C90 forbids array 'f' whose size cannot be evaluated
[-Werror=vla]
cc1: some warnings being treated as errors
Compiler returned: 1
```
Is this intentional or not? GCC 13 doesn't error, nor does Clang 17.
