https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81824
Bug ID: 81824
Summary: Warn for missing attributes with function aliases
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: jsm28 at gcc dot gnu.org
Target Milestone: ---
Consider code like the following:
void foo (void) __attribute__ ((nothrow));
void __foo (void);
void
__foo (void)
{
}
void foo (void) __attribute__ ((weak, alias ("__foo")));
Here, the properties of the nothrow attribute are true for __foo as well as
foo, but code calling __foo (seeing the declarations, not the definition) won't
benefit from the attribute. This is typical of code in glibc: the public
header declares foo with some attributes, the internal header may or may not
have those attributes on the internal version (even if it uses typeof when
declaring the internal function to avoid duplicating the type, that doesn't
replicate function attributes), calls to the internal version don't benefit
from the attributes if missing from the declaration. When compiling the file
with the implementation, it's possible to see that the two functions are the
same, and so that the attributes are missing from one declaration. It would be
useful to have a warning for this case.
Note: this warning is only for attributes relating to the function itself, not
to those relating to a particular name for the function. For example, weak,
alias, visibility attributes are expected to differ between different names and
shouldn't be diagnosed. It would be necessary to work out which existing
function attributes fall in which category.
Note: some relevant attributes may actually apply to the function's type not
the function itself; it's still useful to diagnose when they are missing on one
of the aliased functions.
Note: I don't know how many false positives this warning might have in glibc,
and so whether it would be possible to enable it for all glibc builds or only
for a manual review of code in glibc to try to reduce the number of such cases
of missing attributes.
