[Bug c++/93967] New: switch on exhaustive enum gives control reaches end of non-void function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93967
Bug ID: 93967
Summary: switch on exhaustive enum gives control reaches end of
non-void function
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at cookiesoft dot de
Target Milestone: ---
```
enum class A { X, Y, Z };
int foo(A a) {
switch (a) {
case A::X: return 1;
case A::Y: return 2;
case A::Z: return 3;
}
}
```
`g++ input.cpp`
```
: In function 'int foo(A)':
:9:1: warning: control reaches end of non-void function [-Wreturn-type]
9 | }
| ^
```
The switch is exhaustive and so there is no way that the function reaches the
code path after the switch. Clang does not emit a warning.
This happens on every version of gcc.
Godbolt: https://cpp.godbolt.org/z/Goii_K
[Bug c++/93968] New: -Wswitch-default on exhaustive enum class gives warning
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93968
Bug ID: 93968
Summary: -Wswitch-default on exhaustive enum class gives
warning
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at cookiesoft dot de
Target Milestone: ---
```
enum class A { X, Y, Z };
int foo(A a) {
switch (a) {
case A::X: return 1;
case A::Y: return 2;
case A::Z: return 3;
}
}
```
`g++ -Wswitch-default input.cpp`
```
: In function 'int foo(A)':
:4:12: warning: switch missing default case [-Wswitch-default]
4 | switch (a) {
|^
```
The switch is exhaustive and so there should no warning for a default case, but
when compiling it with `-Wswitch-default` it does emit a warning. Clang does
not.
This happens on every version of gcc.
Godbolt: https://cpp.godbolt.org/z/Goii_K
[Bug c/87365] New: Uninitiliazed variable detection
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87365
Bug ID: 87365
Summary: Uninitiliazed variable detection
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at cookiesoft dot de
Target Milestone: ---
The following snippet does not detect the unitilialized variable
int foo(volatile int cond) {
int a;
if (cond){
a = 0;
} else {
while (cond) {
a++;
}
}
return a;
}
[Bug c/87365] Uninitiliazed variable detection
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87365 --- Comment #1 from gcc at cookiesoft dot de --- The volatile doesn't Change anything. I guess the combination of if and Else-while confuses him
[Bug c++/99362] New: invalid unused result
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99362
Bug ID: 99362
Summary: invalid unused result
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at cookiesoft dot de
Target Milestone: ---
Target: arm
The following code will emit a warning on arm 32 bit compilers:
```
struct S {
[[nodiscard]] S() {}
};
int main() {
S s;
}
```
```
: In function 'int main()':
:6:7: warning: ignoring return value of 'S::S()', declared with
attribute 'nodiscard' [-Wunused-result]
6 | S s;
| ^
:2:19: note: declared here
2 | [[nodiscard]] S() {}
| ^
:6:7: warning: ignoring return value of 'S::S()', declared with
attribute 'nodiscard' [-Wunused-result]
6 | S s;
| ^
:2:19: note: declared here
2 | [[nodiscard]] S() {}
| ^
Compiler returned: 0
```
```
S s = {}
```
does not emit such warning.
Does not emit a warning on x86 compiler though.
Does not emit a warning on 9.x branch, seems to be a regression.
Godbolt link: https://godbolt.org/z/4Kof1x
[Bug c++/99362] invalid unused result
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99362 --- Comment #2 from gcc at cookiesoft dot de --- it's not my code, but a MCVE ;) I'm using [tomlplusplus](https://github.com/marzer/tomlplusplus/blob/master/toml.hpp) and there the constructor is marked as nodiscard. I may file an issue there. So, what about this issue? I guess it's still a bug?!
[Bug c/99810] New: Wrong const evaluation of 64-bit division
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99810
Bug ID: 99810
Summary: Wrong const evaluation of 64-bit division
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at cookiesoft dot de
Target Milestone: ---
Host: x86_64
Target: arm
The following code produces a different result on arm and x86_64:
https://gcc.godbolt.org/z/PPvoscdWa
```
#include
#include
int main() {
printf("%" PRId64 "\n", -621357696 / 100);
}
```
ARM: -2006227456 ( 886B 6600)
X86: -62135769600 ( FFF1 886B 6600)
No single warning is given and I of course would like to see the x86 output,
because that's the right one ;)
[Bug c/99810] Wrong const evaluation of 64-bit division
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99810 --- Comment #3 from gcc at cookiesoft dot de --- I actually haven't, but yes, you're right that it will print out the correct value. I'm somewhat sorry for the noise. Is there a reason, e.g. performance, that the .word is "wrong"?
[Bug c/99810] Wrong const evaluation of 64-bit division
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99810 --- Comment #5 from gcc at cookiesoft dot de --- Alright. Then again, sorry for the noise. I was hunting down a bug and thought I found it with this one... so I have to search further. Thank you everyone!
