[clang] [Clang][Driver] Warn on complex number range incompatibility with GCC (PR #144468)

[Aaron Ballman via cfe-commits]

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@@ -520,6 +520,9 @@ def warn_drv_math_errno_enabled_after_veclib: Warning<
   "math errno enabled by '%0' after it was implicitly disabled by '%1',"
   " this may limit the utilization of the vector library">,
   InGroup<MathErrnoEnabledWithVecLib>;
+def warn_drv_gcc_incompatible_complex_range_override: Warning<
+  "combination of '%0' and '%1' results in complex number calculations incompatible with GCC">,
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AaronBallman wrote:

> Does this mean that if we are going to emit both -Woverriding-option and -Wgcc-compat warnings, the warning messages should be combined into one?

Yeah, I would combine it into one under the `-Woverriding-option` and use a `%select` so that the GCC compatibility parts are optionally emitted.

> If there is a way to determine whether the -Woverriding-option option is specified during driver processing

IIRC, you can do that by adding an explicit compiler option for it, like:
https://github.com/llvm/llvm-project/blob/31bf9348fa10fc95c4a86ef81485652152bf9906/clang/include/clang/Driver/Options.td#L896C5-L896C17
https://github.com/llvm/llvm-project/blob/31bf9348fa10fc95c4a86ef81485652152bf9906/clang/lib/Driver/ToolChains/Clang.cpp#L6455



https://github.com/llvm/llvm-project/pull/144468