[clang] [clang-cl] document correct defaults for `-fms-compatibility-version` / `-fmsc-version` (PR #76418)

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llvmbot wrote:


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@llvm/pr-subscribers-clang

Author: None (h-vetinari)

<details>
<summary>Changes</summary>

The UserManual states wrongly (AFAICT) that these default are not being defined for clang-cl, whereas further up the opposite is stated:

https://github.com/llvm/llvm-project/blob/c86fe3ee0b92934f5d18394d9a0cdc1d3f0eef64/clang/docs/UsersManual.rst#L3375-L3382

I've chosen to follow that wording, as it's the latest related update.

CC @<!-- -->RIscRIpt who recently touched this in b3e6ff331925dde24a4707452d657da0fdf7f588
CC @<!-- -->AaronBallman who cared about this, c.f. 8fc0dcf036bf199b2af2e10a4f81215dbd706daf

---
Full diff: https://github.com/llvm/llvm-project/pull/76418.diff


2 Files Affected:

- (modified) clang/docs/CommandGuide/clang.rst (+1-1) 
- (modified) clang/docs/UsersManual.rst (+2-2) 


``````````diff
diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index e1c872cdc55396..643365215f8759 100644
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -302,7 +302,7 @@ Language Selection and Mode Options
 .. option:: -fmsc-version=
 
  Set ``_MSC_VER``. When on Windows, this defaults to either the same value as
- the currently installed version of cl.exe, or ``1920``. Not set otherwise.
+ the currently installed version of cl.exe, or ``1933``. Not set otherwise.
 
 .. option:: -fborland-extensions
 
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 7c30570437e8b0..32f25be54f5d54 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -4382,11 +4382,11 @@ Execute ``clang-cl /?`` to see a list of supported options:
       -fmerge-all-constants   Allow merging of constants
       -fms-compatibility-version=<value>
                               Dot-separated value representing the Microsoft compiler version
-                              number to report in _MSC_VER (0 = don't define it (default))
+                              number to report in _MSC_VER (0 = don't define it; default is same value as installed cl.exe, or 1933)
       -fms-compatibility      Enable full Microsoft Visual C++ compatibility
       -fms-extensions         Accept some non-standard constructs supported by the Microsoft compiler
       -fmsc-version=<value>   Microsoft compiler version number to report in _MSC_VER
-                              (0 = don't define it (default))
+                              (0 = don't define it; default is same value as installed cl.exe, or 1933)
       -fno-addrsig            Don't emit an address-significance table
       -fno-builtin-<value>    Disable implicit builtin knowledge of a specific function
       -fno-builtin            Disable implicit builtin knowledge of functions

``````````

</details>


https://github.com/llvm/llvm-project/pull/76418