| Issue |
207993
|
| Summary |
clang-tidy check `readability-simplify-boolean-expr` produces bad fixes on C-code when using C23; seems to assume that code is C++
|
| Labels |
|
| Assignees |
|
| Reporter |
Gizzzzmo
|
Since C23 added `true` and `false` as literals, I thought I'd try using `readability-simplify-boolean-expr`, which doesn't work at all with older C standards because true and false are just macros that resolve to 1 and 0, and tidy seems to only match on syntax tree nodes whose type is *actually* `bool`.
And while it does indeed work, the fixes tidy proposes (and applies with `--fix`) seem to assume that the code is C++, as it tries to inject a `static_cast<bool>`:
```c
// simplify_bool_expr.c
#include <stdbool.h>
bool blub(int x)
{
if(x > 10) {
return true;
}
return false;
}
```
```
clang-tidy --checks="-*,readability-simplify*" simplify_bool_expr.c -- --std=c23
3 warnings generated.
/home/jonas/gitprjs/siemens/firmware/xmc4700/clang-tidy-plugins/simplify_bool_expr.c:6:16: warning: redundant boolean literal in conditional return statement [readability-simplify-boolean-expr]
5 | if(x > 10) {
| ~~~~~~~~~~~~
| return static_cast<bool>(x > 10)
6 | return true;
| ~~~~~~~^~~~~
7 | }
| ~
8 |
9 | return false;
| ~~~~~~~~~~~~
Suppressed 2 warnings (2 with check filters).
```
And after running the same command with `--fix` the source file is invalid C:
```c
// simplify_bool.c
#include <stdbool.h>
bool blub(int x)
{
return static_cast<bool>(x > 10);
}
```
Which tidy seems to agree with 🙃:
```
clang-tidy --checks="-*,readability-simplify*" simplify_bool_expr.c -- --std=c23
4 warnings and 2 errors generated.
Error while processing /home/jonas/gitprjs/siemens/firmware/xmc4700/clang-tidy-plugins/simplify_bool_expr.c.
/home/jonas/gitprjs/siemens/firmware/xmc4700/clang-tidy-plugins/simplify_bool_expr.c:5:12: error: use of undeclared identifier 'static_cast' [clang-diagnostic-error]
5 | return static_cast<bool>(x > 10);
| ^~~~~~~~~~~
/home/jonas/gitprjs/siemens/firmware/xmc4700/clang-tidy-plugins/simplify_bool_expr.c:5:24: error: expected _expression_ [clang-diagnostic-error]
5 | return static_cast<bool>(x > 10);
| ^
Suppressed 4 warnings (4 with check filters).
Found compiler error(s).
```
I'm using clang-tidy based on llvm version 22.1.0.
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