Add -Wpoison-system-directories warning

When using clang as a cross-compiler, we should not use system
headers to do the compilation.
This CL adds support of a new warning flag -Wpoison-system-directories which
emits warnings if --sysroot is set and headers from common host system location
are used.
By default the warning is disabled.

The intention of the warning is to catch bad includes which are usually
generated by third party build system not targeting cross-compilation.
Such cases happen in Chrome OS when someone imports a new package or upgrade
one to a newer version from upstream.

Patch by: denik (Denis Nikitin)

llvm-svn: 371785

8 files changed, 39 insertions, 0 deletions

diff --git a/clang/include/clang/Basic/DiagnosticCommonKinds.td b/clang/include/clang/Basic/DiagnosticCommonKinds.td
index 8196a4601c2..1cd62d1e138 100644
--- a/clang/include/clang/Basic/DiagnosticCommonKinds.td
+++ b/clang/include/clang/Basic/DiagnosticCommonKinds.td
@@ -315,4 +315,9 @@ def err_unknown_analyzer_checker_or_package : Error<
     "no analyzer checkers or packages are associated with '%0'">;
 def note_suggest_disabling_all_checkers : Note<
     "use -analyzer-disable-all-checks to disable all static analyzer checkers">;
+
+// Poison system directories.
+def warn_poison_system_directories : Warning <
+  "include location '%0' is unsafe for cross-compilation">,
+  InGroup<DiagGroup<"poison-system-directories">>, DefaultIgnore;
 }
diff --git a/clang/lib/Frontend/InitHeaderSearch.cpp b/clang/lib/Frontend/InitHeaderSearch.cpp
index ad0d2327148..5d877ee9c0d 100644
--- a/clang/lib/Frontend/InitHeaderSearch.cpp
+++ b/clang/lib/Frontend/InitHeaderSearch.cpp
@@ -137,6 +137,13 @@ bool InitHeaderSearch::AddUnmappedPath(const Twine &Path, IncludeDirGroup Group,
   SmallString<256> MappedPathStorage;
   StringRef MappedPathStr = Path.toStringRef(MappedPathStorage);
 
+  // If use system headers while cross-compiling, emit the warning.
+  if (HasSysroot && (MappedPathStr.startswith("/usr/include") ||
+                     MappedPathStr.startswith("/usr/local/include"))) {
+    Headers.getDiags().Report(diag::warn_poison_system_directories)
+        << MappedPathStr;
+  }
+
   // Compute the DirectoryLookup type.
   SrcMgr::CharacteristicKind Type;
   if (Group == Quoted || Group == Angled || Group == IndexHeaderMap) {
diff --git a/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/lib/.keep b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/lib/.keep
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/lib/.keep
diff --git a/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/include/c++/.keep b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/include/c++/.keep
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/include/c++/.keep
diff --git a/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/lib/gcc/.keep b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/lib/gcc/.keep
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/lib/gcc/.keep
diff --git a/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/local/include/.keep b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/local/include/.keep
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/local/include/.keep
diff --git a/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/local/lib/.keep b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/local/lib/.keep
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/clang/test/Frontend/Inputs/sysroot_x86_64_cross_linux_tree/usr/local/lib/.keep
diff --git a/clang/test/Frontend/warning-poison-system-directories.c b/clang/test/Frontend/warning-poison-system-directories.c
new file mode 100644
index 00000000000..018f02db361
--- /dev/null
+++ b/clang/test/Frontend/warning-poison-system-directories.c
@@ -0,0 +1,27 @@
+// System directory and sysroot option causes warning.
+// RUN: %clang -Wpoison-system-directories -target x86_64 -I/usr/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s 2> %t.1.stderr
+// RUN: FileCheck -check-prefix=WARN < %t.1.stderr %s
+// RUN: %clang -Wpoison-system-directories -target x86_64 -cxx-isystem/usr/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s 2> %t.1.stderr
+// RUN: FileCheck -check-prefix=WARN < %t.1.stderr %s
+// RUN: %clang -Wpoison-system-directories -target x86_64 -iquote/usr/local/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s 2> %t.1.stderr
+// RUN: FileCheck -check-prefix=WARN < %t.1.stderr %s
+// RUN: %clang -Wpoison-system-directories -target x86_64 -isystem/usr/local/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s 2> %t.1.stderr
+// RUN: FileCheck -check-prefix=WARN < %t.1.stderr %s
+
+// Missing target but included sysroot still causes the warning.
+// RUN: %clang -Wpoison-system-directories -I/usr/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s 2> %t.2.stderr
+// RUN: FileCheck -check-prefix=WARN < %t.2.stderr %s
+
+// With -Werror the warning causes the failure.
+// RUN: not %clang -Werror=poison-system-directories -target x86_64 -I/usr/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s 2> %t.3.stderr
+// RUN: FileCheck -check-prefix=ERROR < %t.3.stderr %s
+
+// Cros target without sysroot causes no warning.
+// RUN: %clang -Wpoison-system-directories -Werror -target x86_64 -I/usr/include -c -o - %s
+
+// By default the warning is off.
+// RUN: %clang -Werror -target x86_64 -I/usr/include --sysroot %S/Inputs/sysroot_x86_64_cross_linux_tree -c -o - %s
+
+// WARN: warning: include location {{[^ ]+}} is unsafe for cross-compilation [-Wpoison-system-directories]
+
+// ERROR: error: include location {{[^ ]+}} is unsafe for cross-compilation [-Werror,-Wpoison-system-directories]