https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124145
Bug ID: 124145
Summary: Repeat call to constexpr throwing function doesn't
throw
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ivan.lazaric.gcc at gmail dot com
Target Milestone: ---
```
struct S {};
constexpr S tail(S x) {
throw 123;
return x;
}
constexpr inline void head() { tail(S{}); }
consteval {
try {
head();
asm(""); // never reached
} catch (int) {
}
try {
head();
asm(""); // somehow reached
} catch (int) {
}
}
```
Flags used for compilation: -std=c++26
`tail()` and `head()` unconditionally throw an int.
Second call to `head()` doesn't seem to throw, and the asm statement is
reached.
Compiler output:
```
in 'constexpr' expansion of '<lambda()> static()'
<source>:22:1:
22 | }
| ^
<source>:19:5: error: inline assembly is not a constant expression
19 | asm(""); // somehow reached
| ^~~
<source>:19:5: note: only unevaluated inline assembly is allowed in a
'constexpr' function in C++20
Compiler returned: 1
```
Godbolt of example:
https://godbolt.org/z/zaoWEd7jG
