| Issue |
147387
|
| Summary |
Clang does not define `__STRICT_ANSI__` on Windows
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
LIJI32
|
Clang's documents explicitly specify that [`cXX` modes, in contrast to `gnuXX` modes, define `__STRICT_ANSI__`](https://github.com/llvm/llvm-project/blob/122afae10ed28564b64530de571ce8e4ce584b2c/clang/docs/UsersManual.rst#differences-between-various-standard-modes). However, it does not seem to be the case on Windows.
Tested:
```
clang version 20.1.7
Target: x86_64-pc-windows-msvc
Thread model: posix
```
On macOS, running `clang -std=c11 -Xclang -dM -E - < /dev/null` and `clang -std=gnu11 -Xclang -dM -E - < /dev/null` produce a single line of difference – `#define __STRICT_ANSI__ 1`. On Windows, however, both have identical outputs; `__STRICT_ANSI__` is never defined.
This makes it hard to detect the availability on GNU extensions in headers.
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