[libcxx-commits] [libcxx] [AIX][libc++] fopen() does not support the 'x' (exclusive/noreplace) mode suffix. (PR #206498)

[Nikolas Klauser via libcxx-commits]

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@@ -256,8 +256,16 @@ public:
 
   // 27.9.1.4 Members:
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool is_open() const;
+#    if defined(_AIX)
+  _LIBCPP_DIAGNOSE_WARNING(__mode& ios_base::noreplace,
+                           "fstream::open() with noreplace is not supported on AIX; open() will return failure")
+#    endif
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philnik777 wrote:

I'm not sure how big a fan I am of having such platform-specific warnings just in the code randomly. CC @ldionne 

This also needs to be trailing the function.

https://github.com/llvm/llvm-project/pull/206498