https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71603
Bug ID: 71603
Summary: pragma diagnostic pop fails to restore warning level
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
According to the description of #pragma GCC diagnostic push and #pragma GCC
diagnostic pop in the GCC manual:
Causes GCC to remember the state of the diagnostics as of each push, and
restore to that point at each pop. If a pop has no matching push, the
command-line options are restored.
With that, I would expect the following program to cause exactly two warnings,
one for each of -Wformat and -Wshift-overflow, as mentioned in the comments.
But GCC issues four diagnostics instead, indicating that the #pragma pop
directive fails to restore the state of the warnings to that at the point of
each corresponding push.
$ cat t.C && /home/msebor/build/gcc-trunk-svn/gcc/xgcc -B
/home/msebor/build/gcc-trunk-svn/gcc -S -xc t.C
void f (const char *s)
{
#pragma GCC diagnostic warning "-Wformat=1"
__builtin_printf (s, s); // no -Wformat diagnostic expected
#pragma GCC diagnostic push
#pragma GCC diagnostic warning "-Wformat=2"
__builtin_printf (s, s); // -Wformat-nonliteral expected
#pragma GCC diagnostic pop
__builtin_printf (s, s); // no diagnostic expected
}
int x;
int g (void)
{
enum { i = 1 };
#pragma GCC diagnostic warning "-Wshift-overflow=1"
x = i << 31; // no -Wshift-overflow expected
#pragma GCC diagnostic push
#pragma GCC diagnostic warning "-Wshift-overflow=2"
x = i << 31; // -Wshift-overflow expected
#pragma GCC diagnostic pop
x = i << 31; // no warning expected
}
t.C: In function ‘f’:
t.C:9:3: warning: format not a string literal, argument types not checked
[-Wformat-nonliteral]
__builtin_printf (s, s); // -Wformat-nonliteral expected
^~~~~~~~~~~~~~~~
t.C:12:3: warning: format not a string literal, argument types not checked
[-Wformat-nonliteral]
__builtin_printf (s, s); // no diagnostic expected
^~~~~~~~~~~~~~~~
t.C: In function ‘g’:
t.C:28:9: warning: result of ‘1 << 31’ requires 33 bits to represent, but ‘int’
only has 32 bits [-Wshift-overflow=]
x = i << 31; // -Wshift-overflow expected
^~
t.C:31:9: warning: result of ‘1 << 31’ requires 33 bits to represent, but ‘int’
only has 32 bits [-Wshift-overflow=]
x = i << 31; // no warning expected
^~
