<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/125598>125598</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc][signal] fix declaration of sighandler_t
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            nickdesaulniers
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          nickdesaulniers
      </td>
    </tr>
</table>

<pre>
    cross compiling our unit tests (built hermetically) with llvm-libc fails with:
```
llvm-project/libc/test/UnitTest/FPExceptMatcher.cpp:40:3: error: unknown type name 'sighandler_t'; did you mean '__sighandler_t'?
   40 | sighandler_t oldSIGFPEHandler = signal(SIGFPE, &sigfpeHandler);
      | ^~~~~~~~~~~~
      | __sighandler_t
llvm-project/build_aarch64/libc/include/llvm-libc-types/struct_sigaction.h:28:16: note: '__sighandler_t' declared here
   28 | typedef void (*__sighandler_t)(int);
      |                ^
```
it looks like our generated signal.h defines `sighandler_t` with two leading underscores (for some reason, 215c9fa4deac9ec6b4e504843830551f03b60620 seems related). Whatever the problem was should be revisited.
</pre>
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