https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102378
Bug ID: 102378
Summary: missing -Waddress in template code
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
While implementing the suggestion in the review below I noticed that G++ fails
to issue -Waddress in template code even when it could:
https://gcc.gnu.org/pipermail/gcc-patches/2021-September/579082.html
$ cat t.C && gcc -O2 -S -Wall -Waddress t.C
int f ()
{
int a[2];
return &a == 0; // -Waddress (good)
}
template <class T>
int g ()
{
{
int a[2];
return &a == 0; // missing -Waddress
}
{
T t;
return &t == 0; // no -Waddress for type-dependent expr (good)
}
{
T a[2];
return &a == 0; // missing -Waddress
}
}
template <class T>
int h ()
{
{
int a[2];
return &a == 0; // missing -Waddress
}
{
T t;
return &t == 0; // missing -Waddress for T = int
}
{
T a[2];
return &a == 0; // missing -Waddress
}
}
template <int> int h ();
t.C: In function ‘int f()’:
t.C:4:13: warning: the address of ‘a’ will never be NULL [-Waddress]
4 | return &a == 0; // -Waddress (good)
| ~~~^~~~
In contrast, Clang issues three warnings:
t.C:4:11: warning: comparison of address of 'a' equal to a null pointer is
always false [-Wtautological-pointer-compare]
return &a == 0; // -Waddress (good)
^ ~
t.C:12:13: warning: comparison of address of 'a' equal to a null pointer is
always false [-Wtautological-pointer-compare]
return &a == 0; // missing -Waddress
^ ~
t.C:31:13: warning: comparison of address of 'a' equal to a null pointer is
always false [-Wtautological-pointer-compare]
return &a == 0; // missing -Waddress
^ ~
3 warnings generated.
