Author: Fangrui Song
Date: 2019-11-19T13:33:06-08:00
New Revision: 0f34f1b9318e7773fd838b9e0b24f0400616540f

URL: 
https://github.com/llvm/llvm-project/commit/0f34f1b9318e7773fd838b9e0b24f0400616540f
DIFF: 
https://github.com/llvm/llvm-project/commit/0f34f1b9318e7773fd838b9e0b24f0400616540f.diff

LOG: Merging r367981:

------------------------------------------------------------------------
r367981 | maskray | 2019-08-05 23:25:32 -0700 (Mon, 05 Aug 2019) | 27 lines

[Driver] Prioritize SYSROOT/usr/include over RESOURCE_DIR/include on linux-musl

On a musl-based Linux distribution, stdalign.h stdarg.h stdbool.h stddef.h 
stdint.h stdnoreturn.h are expected to be provided by musl (/usr/include), 
instead of RESOURCE_DIR/include.
Reorder RESOURCE_DIR/include to fix the search order problem.
(Currently musl doesn't provide stdatomic.h. stdatomic.h is still found in 
RESOURCE_DIR/include.)

gcc on musl has a similar search order:

```
 /usr/lib/gcc/x86_64-alpine-linux-musl/8.3.0/../../../../include/c++/8.3.0
 
/usr/lib/gcc/x86_64-alpine-linux-musl/8.3.0/../../../../include/c++/8.3.0/x86_64-alpine-linux-musl
 
/usr/lib/gcc/x86_64-alpine-linux-musl/8.3.0/../../../../include/c++/8.3.0/backward
 /usr/local/include
 /usr/include/fortify
 /usr/include
 /usr/lib/gcc/x86_64-alpine-linux-musl/8.3.0/include
```

This is different from a glibc-based distribution where RESOURCE_DIR/include is 
placed before SYSROOT/usr/include.

According to the maintainer of musl:

> musl does not support use/mixing of compiler-provided std headers with its 
> headers, and intentionally has no mechanism for communicating with such 
> headers as to which types have already been defined or still need to be 
> defined. If the current include order, with clang's headers before the libc 
> ones, works in some situations, it's only by accident.

Reviewed by: phosek

Differential Revision: https://reviews.llvm.org/D65699
------------------------------------------------------------------------

Added: 
    clang/test/Driver/linux-musl-header-search.cpp

Modified: 
    clang/lib/Driver/ToolChains/Linux.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Driver/ToolChains/Linux.cpp 
b/clang/lib/Driver/ToolChains/Linux.cpp
index d900508ad938..7f59bc77f526 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -658,11 +658,11 @@ void Linux::AddClangSystemIncludeArgs(const ArgList 
&DriverArgs,
   if (!DriverArgs.hasArg(options::OPT_nostdlibinc))
     addSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/local/include");
 
-  if (!DriverArgs.hasArg(options::OPT_nobuiltininc)) {
-    SmallString<128> P(D.ResourceDir);
-    llvm::sys::path::append(P, "include");
-    addSystemInclude(DriverArgs, CC1Args, P);
-  }
+  SmallString<128> ResourceDirInclude(D.ResourceDir);
+  llvm::sys::path::append(ResourceDirInclude, "include");
+  if (!DriverArgs.hasArg(options::OPT_nobuiltininc) &&
+      (!getTriple().isMusl() || DriverArgs.hasArg(options::OPT_nostdlibinc)))
+    addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
 
   if (DriverArgs.hasArg(options::OPT_nostdlibinc))
     return;
@@ -860,6 +860,9 @@ void Linux::AddClangSystemIncludeArgs(const ArgList 
&DriverArgs,
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/include");
 
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include");
+
+  if (!DriverArgs.hasArg(options::OPT_nobuiltininc) && getTriple().isMusl())
+    addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
 }
 
 static std::string DetectLibcxxIncludePath(llvm::vfs::FileSystem &vfs,

diff  --git a/clang/test/Driver/linux-musl-header-search.cpp 
b/clang/test/Driver/linux-musl-header-search.cpp
new file mode 100644
index 000000000000..9fee03600682
--- /dev/null
+++ b/clang/test/Driver/linux-musl-header-search.cpp
@@ -0,0 +1,39 @@
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-linux-musl -stdlib=libc++ \
+// RUN:     -ccc-install-dir %S/Inputs/basic_linux_tree/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     --sysroot=%S/Inputs/basic_linux_libcxx_tree --gcc-toolchain= \
+// RUN:   | FileCheck --check-prefix=CHECK-X86-64-LIBCXX %s
+
+// RESOURCE_DIR/include comes after /usr/include on linux-musl.
+// This is 
diff erent from a glibc-based distribution.
+// CHECK-X86-64-LIBCXX: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
+// CHECK-X86-64-LIBCXX: "-isysroot" "[[SYSROOT:[^"]+]]"
+// CHECK-X86-64-LIBCXX: "-internal-isystem" "[[SYSROOT]]/usr/include/c++/v1"
+// CHECK-X86-64-LIBCXX: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-X86-64-LIBCXX: "-internal-externc-isystem" "[[SYSROOT]]/usr/include"
+// CHECK-X86-64-LIBCXX: "-internal-isystem" "[[RESOURCE_DIR]]{{/|\\\\}}include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only -nobuiltininc 2>&1 
\
+// RUN:     -target x86_64-linux-musl \
+// RUN:     -ccc-install-dir %S/Inputs/basic_linux_tree/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     --sysroot=%S/Inputs/basic_linux_libcxx_tree --gcc-toolchain= \
+// RUN:   | FileCheck --check-prefix=CHECK-NOBUILTININC %s
+
+// CHECK-NOBUILTININC: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
+// CHECK-NOBUILTININC-NOT: "-internal-isystem" 
"[[RESOURCE_DIR]]{{/|\\\\}}include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only -nostdlibinc 2>&1 \
+// RUN:     -target x86_64-linux-musl \
+// RUN:     -ccc-install-dir %S/Inputs/basic_linux_tree/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     --sysroot=%S/Inputs/basic_linux_libcxx_tree --gcc-toolchain= \
+// RUN:   | FileCheck --check-prefix=CHECK-NOSTDLIBINC %s
+
+// CHECK-NOSTDLIBINC: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
+// CHECK-NOSTDLIBINC-NOT: "-internal-externc-isystem"
+// CHECK-NOSTDLIBINC-NOT: "-internal-isystem"
+// CHECK-NOSTDLIBINC: "-internal-isystem" "[[RESOURCE_DIR]]{{/|\\\\}}include"
+// CHECK-NOSTDLIBINC-NOT: "-internal-externc-isystem"
+// CHECK-NOSTDLIBINC-NOT: "-internal-isystem"


        
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