https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121907
Bug ID: 121907
Summary: -Wauto-as-storage-class: New diagnostic
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: foss+...@alejandro-colomar.es
Target Milestone: ---
Given that auto now means __auto_type, we should diagnose old uses of it as a
storage-class specifier.
The current hybrid is going to cause confusion in programmers (it already
confuses me, FWIW). It seems to be the new 'static', in the sense of being an
overloaded keyword. Could we please have this diagnostic and have it in
-Wextra (at least)?
It should diagnose lines 10 and 13 below.
BTW, line 10 should not be an error; those two uses of auto are different and
valid, I think. That shows precisely how much this hybrid auto confuses
programmers (of compilers).
alx@debian:~/tmp/auto$ cat scs.c | nl -ba
1 int typedef i_t; // -Wold-style-declaration
2
3 int
4 main(void)
5 {
6 int static is = 0; // -Wold-style-declaration
7 auto static as = 0; // XXX: Should be
-Wold-style-declaration
8 static static ss = 0; // -Wduplicate-decl-specifier (GCC
error)
9 int auto ia = 0; // -Wold-style-declaration (Clang
error)
10 auto auto aa = 0; // XXX: Why error? Also, would like
-Wauto-as-storage-class
11 static auto sa = 0;
12 int int ii = 0; // error
13 auto int ai = 0; // XXX: Would like
-Wauto-as-storage-class
14 static int si = 0;
15 }
alx@debian:~/tmp/auto$ gcc -Wall -Wextra -std=c23 scs.c -Wno-unused
scs.c:1:1: warning: ‘typedef’ is not at beginning of declaration
[-Wold-style-declaration]
1 | int typedef i_t; // -Wold-style-declaration
| ^~~
scs.c: In function ‘main’:
scs.c:6:9: warning: ‘static’ is not at beginning of declaration
[-Wold-style-declaration]
6 | int static is = 0; // -Wold-style-declaration
| ^~~
scs.c:8:9: error: duplicate ‘static’
8 | static static ss = 0; // -Wduplicate-decl-specifier (GCC
error)
| ^~~~~~
scs.c:8:25: error: type defaults to ‘int’ in declaration of ‘ss’
[-Wimplicit-int]
8 | static static ss = 0; // -Wduplicate-decl-specifier (GCC
error)
| ^~
scs.c:9:9: warning: ‘auto’ is not at beginning of declaration
[-Wold-style-declaration]
9 | int auto ia = 0; // -Wold-style-declaration (Clang
error)
| ^~~
scs.c:10:9: error: duplicate ‘auto’
10 | auto auto aa = 0; // XXX: Why error? Also, would like
-Wauto-as-storage-class
| ^~~~
scs.c:12:17: error: two or more data types in declaration specifiers
12 | int int ii = 0; // error
| ^~~
