Cannot build compiler_builtins with Visual Studio 2019 Build Tools

[ehuss]

Trying to build rustc with Visual Studio 2019 Build Tools results in the following error:

running: "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\BuildTools\\VC\\Tools\\MSVC\\14.21.27702\\bin\\HostX64\\x64\\cl.exe" "/nologo" "/MT" "/O2" "/Zl" "/D__func__=__FUNCTION__" "/FoC:\\Proj\\rust\\build\\x86_64-pc-windows-msvc\\stage0-std\\x86_64-pc-windows-msvc\\release\\build\\compiler_builtins-21b4e69466e2594a\\out\\divdc3.o" "/c" "C:\\Proj\\rust\\src/llvm-project/compiler-rt\\lib/builtins\\divdc3.c"
divdc3.c
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.21.27702\include\xkeycheck.h(45): warning C4005: 'bool': macro redefinition
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.21.27702\include\stdbool.h(15): note: see previous definition of 'bool'
C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.21.27702\include\xkeycheck.h(47): fatal error C1189: #error:  The C++ Standard Library forbids macroizing the keyword "bool". Enable warning C4005 to find the forbidden define.
exit code: 2

I've tried version versions 16.1.1 and 16.1.3 on different machines with the same result.

Visual Studio 2017 Build Tools work fine.

Is there some magic incantation I'm missing?

[scottmcm]

I get this as well.

I've been hacking around it with

--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -179,8 +179,9 @@ pub fn std_cargo(builder: &Builder<'_>,
     // `compiler-rt` is located.
     let compiler_builtins_root = builder.src.join("src/llvm-project/compiler-rt");
     let compiler_builtins_c_feature = if compiler_builtins_root.exists() {
-        cargo.env("RUST_COMPILER_RT_ROOT", &compiler_builtins_root);
-        " compiler-builtins-c".to_string()
+        //cargo.env("RUST_COMPILER_RT_ROOT", &compiler_builtins_root);
+        //" compiler-builtins-c".to_string()
+        String::new() // HACK! the c builtins don't build for me
     } else {
         String::new()
     };

I think this was introduced in #60981, so cc @alexcrichton

[alexcrichton]

I don't think that anything is being missed here. This is probably a bug with either:

• An upstream compiler-rt bug that needs to be fixed
• A bug with how we build compiler-rt since we're not using the standard build system

The former may already even be fixed upstream, the latter is probably some missing /D flag we're not passing and would require inspecting the source. In both cases the source needs to be inspected likely :)

[Zoxc]

This patch was applied to our compiler-rt fork, but it was lost somehow, breaking VS 2019 builds.