Frontend: support -I=path for sysroot expansion

From the GCC manpage:

  -I dir
    ... If dir begins with =, then the = will be replaced by the sysroot prefix;
    see --sysroot and -isysroot.

Add support to expand the `=` as a prefix of the include path with the sysroot
if specified.  `-isysroot` takes precedence over `--sysroot` as the normal
argument behaviour occurs.  The ordering of the `-isysroot` is relevant to the
path substituted.  If no `--sysroot=` or `-isysroot` option is present, the = is
not expanded.

Resolves PR26965!

llvm-svn: 268777

1 files changed, 14 insertions, 2 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 0b154b6743c..a97dc92adfa 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1278,6 +1278,8 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
 
   // Add -I..., -F..., and -index-header-map options in order.
   bool IsIndexHeaderMap = false;
+  bool IsSysrootSpecified =
+      Args.hasArg(OPT__sysroot_EQ) || Args.hasArg(OPT_isysroot);
   for (const Arg *A : Args.filtered(OPT_I, OPT_F, OPT_index_header_map)) {
     if (A->getOption().matches(OPT_index_header_map)) {
       // -index-header-map applies to the next -I or -F.
@@ -1288,8 +1290,18 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
     frontend::IncludeDirGroup Group =
         IsIndexHeaderMap ? frontend::IndexHeaderMap : frontend::Angled;
 
-    Opts.AddPath(A->getValue(), Group,
-                 /*IsFramework=*/A->getOption().matches(OPT_F), true);
+    bool IsFramework = A->getOption().matches(OPT_F);
+    std::string Path = A->getValue();
+
+    if (IsSysrootSpecified && !IsFramework && A->getValue()[0] == '=') {
+      SmallString<32> Buffer;
+      llvm::sys::path::append(Buffer, Opts.Sysroot,
+                              llvm::StringRef(A->getValue()).substr(1));
+      Path = Buffer.str();
+    }
+
+    Opts.AddPath(Path.c_str(), Group, IsFramework,
+                 /*IgnoreSysroot*/ true);
     IsIndexHeaderMap = false;
   }