[Bug c/108518] New: Format-overflow warning using `*.s` directive with null but zero-length string
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108518
Bug ID: 108518
Summary: Format-overflow warning using `*.s` directive with
null but zero-length string
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: aaron at aarongraham dot com
Target Milestone: ---
https://godbolt.org/z/YGra91Woa
#include
int main() {
// This causes a format-overflow warning, but it
// should not warn if size() is 0
printf("%.*s\n", 0, (char*)0);
}
The warning is:
: In function 'int main()':
:6:13: warning: '%.*s' directive argument is null [-Wformat-overflow=]
6 | printf("%.*s\n", 0, (char*)0);
| ^~~~
I see this commonly when using std::string_view with printf. In cases where it
knows that you're passing a default-constructed string_view it produces this
warning.
It should not produce this warning if the length being printed is 0.
[Bug libstdc++/106802] New: Comparators in don't work with orderings in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106802
Bug ID: 106802
Summary: Comparators in don't work with orderings
in
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: aaron at aarongraham dot com
Target Milestone: ---
gcc does not allow this to compile:
std::less<>{}(std::strong_ordering::less, 0);
Even though `std::strong_ordering::less < 0` is perfectly legal and
well-formed.
It will compile this (but clang will not):
std::less<>{}(std::strong_ordering::less, nullptr);
Godbolt link: https://gcc.godbolt.org/z/9ed16KbhP
[Bug c++/100322] New: Switching from std=c++17 to std=c++20 causes performance regression in relationals
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100322
Bug ID: 100322
Summary: Switching from std=c++17 to std=c++20 causes
performance regression in relationals
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: aaron at aarongraham dot com
Target Milestone: ---
Experiment here: https://godbolt.org/z/PT73cn5e5
#include
using clk = std::chrono::steady_clock;
bool compare_count(clk::duration a, clk::duration b) {
return a.count() > b.count();
}
bool compare(clk::duration a, clk::duration b) {
return a > b;
}
Compiling with -std=c++17 I get:
_Z13compare_countNSt6chrono8durationIxSt5ratioILx1ELx10S3_:
cmp r2, r0
sbcsr3, r3, r1
ite lt
movlt r0, #1
movge r0, #0
bx lr
_Z7compareNSt6chrono8durationIxSt5ratioILx1ELx10S3_:
cmp r2, r0
sbcsr3, r3, r1
ite lt
movlt r0, #1
movge r0, #0
bx lr
Compiling with -std=c++20 I get:
_Z13compare_countNSt6chrono8durationIxSt5ratioILx1ELx10S3_:
cmp r2, r0
sbcsr3, r3, r1
ite lt
movlt r0, #1
movge r0, #0
bx lr
_Z7compareNSt6chrono8durationIxSt5ratioILx1ELx10S3_:
cmp r1, r3
it eq
cmpeq r0, r2
beq .L4
cmp r0, r2
sbcsr3, r1, r3
bge .L5
mov r0, #-1
.L3:
cmp r0, #0
ite le
movle r0, #0
movgt r0, #1
bx lr
.L4:
movsr0, #0
b .L3
.L5:
movsr0, #1
b .L3
(Note that clang doesn't have this problem)
[Bug libstdc++/100259] New: ODR violations in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100259 Bug ID: 100259 Summary: ODR violations in Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: aaron at aarongraham dot com Target Milestone: --- Current implementation in has functions that violate ODR: std::experimental::net::ip::make_error_code std::experimental::net::ip::make_error_condition std::experimental::net::ip::make_network_v4 It seems these should be inline and/or constexpr. There are probably others.
