[libc] Mark operator== const to avoid ambiguity in C++20.

[bazuzi]

C++20 will automatically generate an operator== with reversed operand order, which is ambiguous with the written operator== when one argument is marked const and the other isn't.

This operator currently triggers -Wambiguous-reversed-operator at usage site libc/test/UnitTest/PrintfMatcher.cpp:28.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Samira Bazuzi (bazuzi)

Changes

C++20 will automatically generate an operator== with reversed operand order, which is ambiguous with the written operator== when one argument is marked const and the other isn't.

This operator currently triggers -Wambiguous-reversed-operator at usage site libc/test/UnitTest/PrintfMatcher.cpp:28.

---

Full diff: https://github.com/llvm/llvm-project/pull/68805.diff

1 Files Affected:

• (modified) libc/src/stdio/printf_core/core_structs.h (+1-1)

diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index e96bc4dc0f8dd3c..88a13703fd94761 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -53,7 +53,7 @@ struct FormatSection {
 
   // This operator is only used for testing and should be automatically
   // optimized out for release builds.
-  bool operator==(const FormatSection &other) {
+  bool operator==(const FormatSection &other) const {
     if (has_conv != other.has_conv)
       return false;
 

[bazuzi]

@michaelrj-google Are you available to review (and eventually hit merge) on this? I don't have write access to add reviewers or merge.