https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95354
Bug ID: 95354
Summary: GCC misuse "nonnull-attribute" option and can not
detect it as UB as well
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: haoxintu at gmail dot com
Target Milestone: ---
This case test.cc
#include<iostream>
#include<cstddef>
void has_nonnull_argument(__attribute__((nonnull)) int *p) {
;
}
int main () {
has_nonnull_argument(NULL);
std::cout << "ok" << std::endl;
return 0;
}
in GCC-trunk
$./g++ -fsanitize=undefined test.cc ; ./a.out
test.cc:3:57: warning: ‘nonnull’ attribute only applies to function types
[-Wattributes]
3 | void has_nonnull_argument(__attribute__((nonnull)) int *p) {
| ^
ok
$./g++ -fsanitize=nonull-attribute test.cc ; ./a.out
test.cc:3:57: warning: ‘nonnull’ attribute only applies to function types
[-Wattributes]
3 | void has_nonnull_argument(__attribute__((nonnull)) int *p) {
| ^
ok
in Clang-trunk
$clang++ -fsanitize=nonnull-attribute test.cc ; ./a.out
est.cc:7:30: warning: null passed to a callee that requires a non-null argument
[-Wnonnull]
has_nonnull_argument(NULL);
~~~~^
1 warning generated.
test.cc:7:26: runtime error: null pointer passed as argument 1, which is
declared to never be null
test.cc:3:42: note: nonnull attribute specified here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior test.cc:7:26 in
ok
According to the description in
https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
for "-fsanitize=nonull-attribute", it says "This option enables instrumentation
of calls, checking whether null values are not passed to arguments marked as
requiring a non-null value by the nonnull function attribute."
I guess the warning message by GCC may also incorrect, the correct one should
look like in Clang produced.
I have tested them in recent GCC versions including GCC-8, GCC-9, and GCC-10,
they have the same symptom as well.
My GCC version is
$g++ --version
g++ (GCC) 11.0.0 20200526 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
