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[Driver][SYCL] Do not imply defaultlib msvcrt for Linux based driver on Windows #3827

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Merged
merged 1 commit into from
Jun 3, 2021
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[Driver][SYCL] Do not imply defaultlib msvcrt for Linux based driver on Windows #3827

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1 change: 0 additions & 1 deletion clang/lib/Driver/ToolChains/Clang.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4663,7 +4663,6 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
if (AuxT.isWindowsMSVCEnvironment()) {
CmdArgs.push_back("-D_MT");
CmdArgs.push_back("-D_DLL");
CmdArgs.push_back("--dependent-lib=msvcrt");
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It is hard to tell, why the new code would work properly. It does not seem correct to me now.
The idea of the line that is removed here was to enforce dynamic MSVC RT with -fsycl switch for clang++ driver.

For CL mode the MSVC RT is set in addClangCLArgs() and CL allows either /MD (msvcrt) or /MDd (msvcrtd).
The line that was removed in this patch is for 'clang++' driver, which does not allow setting /MDd, and thus the only option for -fsycl is msvcrt.

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What RT is used in the patched compiler (i.e. clang++ -fsycl test.cpp)? If that is libcmt (which is by default), then there may be errors caused by using msvcrt in SYCL and libcmt in test.obj

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The default library (msvcrt) used is passed to the link step via -defaultlib:

> clang++ -fsycl --target=x86_64-pc-windows-msvc ~/a.cpp -### 2>&1 | grep msvcrt "link.exe" "-out:a.exe" "-defaultlib:msvcrt" "-defaultlib:oldnames" "-defaultlib:sycl.lib" "/IGNORE:4078" "-libpath:lib/amd64" "-libpath:atlmfc/lib/amd64" "-nologo" "/tmp/a-ca1b1c.o" "/tmp/a-028002.o"

The use of the -defaultlib option is used for clang++ and the embedded default directives are used for clang-cl.

}
}
}
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2 changes: 1 addition & 1 deletion clang/test/Driver/sycl-MD-default.cpp
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Expand Up @@ -5,7 +5,7 @@
// RUN: %clangxx -### -fsycl -c -target x86_64-unknown-windows-msvc %s 2>&1 \
// RUN: | FileCheck -check-prefix=CHK-DEFAULT %s
// CHK-DEFAULT-NOT: "-fsycl-is-device" {{.*}} "-D_MT" "-D_DLL"
// CHK-DEFAULT: "-fsycl-is-host"{{.*}} "-D_MT" "-D_DLL" "--dependent-lib=msvcrt{{d*}}" {{.*}}
// CHK-DEFAULT: "-fsycl-is-host"{{.*}} "-D_MT" "-D_DLL"

// RUN: %clang_cl -### -fsycl -c %s 2>&1 \
// RUN: | FileCheck -check-prefix=CHK-DEFAULT-CL %s
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