https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111289
Bug ID: 111289
Summary: Unwarranted -Wanalyzer-va-arg-type-mismatch warning
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: bruno at clisp dot org
Target Milestone: ---
Created attachment 55842
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55842&action=edit
test case foo.c
On the attached program, gcc 13.2.0 with analyzer produces a warning:
$ gcc -fanalyzer -O2 -S foo.c
foo.c: In function ‘do_open’:
foo.c:13:10: warning: ‘va_arg’ expected ‘mode_t’ {aka ‘unsigned int’} but
received ‘int’ for variadic argument 1 of ‘arg’ [CWE-686]
[-Wanalyzer-va-arg-type-mismatch]
13 | mode_t mode = va_arg (arg, mode_t);
| ^~~~
‘main’: events 1-2
|
| 20 | main ()
| | ^~~~
| | |
| | (1) entry to ‘main’
| 21 | {
| 22 | do_open ("nonexist.ent/", 0600);
| | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | |
| | (2) calling ‘do_open’ from ‘main’ with 1 variadic argument
|
+--> ‘do_open’: events 3-4
|
| 8 | do_open (char const *name, ...)
| | ^~~~~~~
| | |
| | (3) entry to ‘do_open’
|......
| 13 | mode_t mode = va_arg (arg, mode_t);
| | ~~~~
| | |
| | (4) ‘va_arg’ expected ‘mode_t’ {aka ‘unsigned
int’} but received ‘int’ for variadic argument 1 of ‘arg’
|
There is no reason to warn here, because
1) ISO C 99 § 7.15.1.1.(2) says "... the behavior is undefined, except for the
following cases:
— one type is a signed integer type, the other type is the corresponding
unsigned integer type, and the value is representable in both types;
— ..."
Likewise ISO C 23 § 7.16.1.1.(2).
2) The argument that gets passed is an 'int'. The other type, mode_t, is
'unsigned int'. The argument is a constant, and its value 0600 is representable
both as 'int' and as 'unsigned int'.
