[libc-commits] [PATCH] D71094: [libc] Add implementation of errno and define the other macros of errno.h.

[Fangrui Song via Phabricator via libc-commits]

MaskRay added inline comments.


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Comment at: libc/config/linux/api.td:34
+    extern int *__errno_location();
+    #define errno *__errno_location()
+  }];
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sivachandra wrote:
> MaskRay wrote:
> > `()`
> > 
> > Otherwise `errno[0]` is incorrect.
> We don't want to put it in parenthesis because we want to error on uses like `errno[0]`. `errno` is supposed to be an lvalue of int type and allowing `errno[0]` actually amounts to leaking implementation detail.
I know errno[0] will be an error anyway.

However, this breaks grouping: `*__errno_location()[0]`

You also don't want `3 errno` to be treated as `3*__errno_location()`, do you?


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Comment at: libc/src/errno/llvmlibc_errno.h:14
+// public header.
+extern int &llvmlibc_errno;
+
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I don't think this will work. In the test translation unit, the compiler does not know that `llvmlibc_errno` is bound to a thread-local variable.

Even in the definition site, it's not clear to me that a reference to a thread-local variable will guarantee to work.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71094/new/

https://reviews.llvm.org/D71094