[Bug libstdc++/101203] Remove unnecessary empty check in std::function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101203 Toni Neubert changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution|--- |WONTFIX --- Comment #5 from Toni Neubert --- Improvement not possible for all environment.
[Bug ipa/106921] [11/12/13/14 Regression] -O1 and -fipa-icf -fpartial-inlining causes wrong code since r11-4987-g602c6cfc79ce4ae6
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106921 --- Comment #8 from Toni Neubert --- Hello, I just wanted to ask what the state of this bug is? I think that incorrectly compiled code should be much more important than anything else since any system can be affected without even knowing it. I know that a lot of things happen here on a voluntary basis and I value that very much. What can we do to give such bugs a hire priority or help to solve such things?
[Bug c++/106921] [11/12/13 Regression] -O1 and -fipa-icf -fpartial-inlining causes wrong code since r11-4987-g602c6cfc79ce4ae6
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106921 --- Comment #3 from Toni Neubert --- Any update on this? Which compiler flag triggers this bug exactly? Or is it a complex combination multiple?
[Bug c++/106921] New: [11/12.1] -O1 and -fipa-icf -fpartial-inlining causes wrong code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106921
Bug ID: 106921
Summary: [11/12.1] -O1 and -fipa-icf -fpartial-inlining causes
wrong code
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
Short summary:
The following code returns 1 if compiled with -O2 (which is wrong) and does
return 0 if compiled without optimization.
```
#include
#include
#include
#define GCC_VERSION (__GNUC__ * 1 \
+ __GNUC_MINOR__ * 100 \
+ __GNUC_PATCHLEVEL__)
static_assert(GCC_VERSION == 110300);
template
class bitset {
private:
using word_t = size_t;
static constexpr size_t bits_per_word = sizeof(word_t) * 8;
static constexpr size_t number_of_words = (Bits / bits_per_word) + (((Bits %
bits_per_word) == 0) ? 0 : 1);
public:
bool all_first(size_t n) const {
{
if (n > Bits) {
#ifdef RETURN_INSTEAD_TERMINATE
return false;
#else
std::terminate();
#endif
}
size_t i = 0;
for (; n > bits_per_word; n -= bits_per_word, i++) {
if (words_[i] != ~word_t{0}) {
return false;
}
}
word_t last_word = words_[i];
for (; n != 0; n--) {
if ((last_word & 1) != 1) {
return false;
}
last_word >>= 1;
}
return true;
}
}
void fill() noexcept {
for (auto& word : words_) {
word = ~word_t{0};
}
}
private:
std::array words_{};
};
volatile int X = 0;
int main() {
if (X == 1) {
bitset<123> bitset;
static_cast(bitset.all_first(123));
} else {
bitset<256> bitset;
bitset.fill();
if (!bitset.all_first(255)) {
return 1;
}
}
return 0;
}
```
See: https://gcc.godbolt.org/z/bEexjrKP4
This issue does not exist in GCC 10 or GCC > 12.1. I couldn't test if it does
work in GCC 11.3.1 (or the trunk of it).
Additional:
* I could also trigger the issue with -O1 -fipa-icf -fpartial-inlining
* If we do a return false instead of a std::terminate, no wrong code is
generated.
I am sorry, but I couldn't reduced the code any further - this already took so
much time to figure out it is a compiler bug.
[Bug c++/105060] New: [10/11] ICE with consteval function: internal compiler error: in cp_gimplify_expr, at cp/cp-gimplify.c:14879 with keep-inline-functions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105060
Bug ID: 105060
Summary: [10/11] ICE with consteval function: internal compiler
error: in cp_gimplify_expr, at cp/cp-gimplify.c:14879
with keep-inline-functions
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
Compiled with g++ 10/11 and -fkeep-inline-functions -std=c++20. Doesn't seem to
happen with current trunk.
ERROR:
: In constructor 'consteval
basic_format_string::basic_format_string(const S&) [with S = char [1];
Args = {char, }]':
:19:5: internal compiler error: in gimplify_expr, at gimplify.c:14879
19 | if (!check()) {
| ^~
0x1786229 internal_error(char const*, ...)
???:0
0x678608 fancy_abort(char const*, int, char const*)
???:0
0xab0f92 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
???:0
0xab1068 gimplify_stmt(tree_node**, gimple**)
???:0
0xaaebb2 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
???:0
0xab1068 gimplify_stmt(tree_node**, gimple**)
???:0
0xab212b gimplify_body(tree_node*, bool)
???:0
0xab259f gimplify_function_tree(tree_node*)
???:0
0x943cf7 cgraph_node::analyze()
???:0
0x94707d symbol_table::finalize_compilation_unit()
???:0
CODE:
template
struct type_identity {
using type = T;
};
template
using type_identity_t = typename type_identity::type;
constexpr int check() {
return {};
}
template
class basic_format_string {
public:
template
consteval basic_format_string(const S& s) {
if (!check()) {
}
}
};
template
using format_string = basic_format_string...>;
template
void test(format_string format_str, const Args&... args) {}
enum { Blue };
void g() {
test("", Blue);
}
See: https://gcc.godbolt.org/z/M7v96YPn1
[Bug libstdc++/101203] Remove unnecessary empty check in std::function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101203 --- Comment #3 from Toni Neubert --- Thank you Jonathan for your fast answer. To sad but the shared library issue seems valid. Can shared libraries exist is a freestanding environment (like a bare-metal microcontroller running without OS)? So there could maybe an optimization for some targets?
[Bug libstdc++/101203] New: Remove unnecessary empty check in std::function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101203
Bug ID: 101203
Summary: Remove unnecessary empty check in std::function
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
Hello,
this empty() check in std_function.h:
https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/include/bits/std_function.h#L558
_Res
operator()(_ArgTypes... __args) const
{
if (_M_empty())
__throw_bad_function_call();
return _M_invoker(_M_functor, std::forward<_ArgTypes>(__args)...);
}
can, as I assume, be removed to gain better performance.
An empty, default constructed std::function could be initialized with
__throw_bad_function_call() instead with nullptr/zeros.
If std::function::operator()(...) gets called, still
__throw_bad_function_call() would get called as before.
The implementation of `explicit operator bool()` or better `_M_empty()` would
then check if the function is initialized with the address of
__throw_bad_function_call.
This would be a similar technic as used in std::any:
https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/include/experimental/any#L436
[Bug c++/97237] [10/11 Regression] static_assert does not accept fpermissive code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97237 Toni Neubert changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |WONTFIX --- Comment #5 from Toni Neubert --- Closed this in favor of other bugs. This isn't necessary at all. Sorry for your time.
[Bug c++/97610] New: [10/11] template argument deduction fails for function with defaulted lambda as non-type-template parameter
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97610
Bug ID: 97610
Summary: [10/11] template argument deduction fails for function
with defaulted lambda as non-type-template parameter
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
The following code (with C++20 enabled):
template
constexpr auto nested() {
return 1;
}
template
constexpr void test() {
static_assert(nested());
}
--
Fails with:
: In function 'constexpr void test()':
:8:30: error: no matching function for call to 'nested()'
8 | static_assert(nested());
| ^
:2:16: note: candidate: 'template > constexpr auto
nested()'
2 | constexpr auto nested() {
|^~
:2:16: note: template argument deduction/substitution failed:
--
* same error happens if nested() has template as
this template parameters
* if the template non-type parameter of nested() is defaulted to 1, it compiles
* if test() is not a template function, it compiles
* if static_assert(nested<[]{}>()); is used, it compiles
[Bug c++/97237] [10/11 Regression] static_assert does not accept fpermissive code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97237
--- Comment #4 from Toni Neubert ---
This code seems to fail for the same reason:
constexpr int get() {
[[maybe_unused]] auto i = 1 << 32;
return 0;
}
template
constexpr int test() {
return a;
}
constexpr int t1 = get();
constexpr int t2 = test();
[Bug c++/97237] New: [10/11 Regression] static_assert does not accept fpermissive code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97237
Bug ID: 97237
Summary: [10/11 Regression] static_assert does not accept
fpermissive code
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
The following valid code:
constexpr bool test() {
auto i = 1 << 132;
return true;
}
static_assert(test());
Build with GCC -fpermissive does compile in GCC 9 but not in 10/11:
> non-constant condition for static assertion
See: https://gcc.godbolt.org/z/r85zvP
But this code is valid in all versions:
constexpr bool test() {
auto i = 1 << 132;
return true;
}
constexpr auto t = test();
static_assert(t);
