Add support for sysroot-relative system header search paths (#82084)

Clang supported header searchpaths of the form `-I =/path`, relative to
the sysroot if one is passed, but did not implement that behavior for
`-iquote`, `-isystem`, or `-idirafter`.

This implements the `=` portion of the behavior implemented by GCC for
these flags described in
https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html.

1 files changed, 28 insertions, 15 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 2a21a9d..0df6a82 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3191,6 +3191,22 @@ static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
   bool IsIndexHeaderMap = false;
   bool IsSysrootSpecified =
       Args.hasArg(OPT__sysroot_EQ) || Args.hasArg(OPT_isysroot);
+
+  // Expand a leading `=` to the sysroot if one was passed (and it's not a
+  // framework flag).
+  auto PrefixHeaderPath = [IsSysrootSpecified,
+                           &Opts](const llvm::opt::Arg *A,
+                                  bool IsFramework = false) -> std::string {
+    assert(A->getNumValues() && "Unexpected empty search path flag!");
+    if (IsSysrootSpecified && !IsFramework && A->getValue()[0] == '=') {
+      SmallString<32> Buffer;
+      llvm::sys::path::append(Buffer, Opts.Sysroot,
+                              llvm::StringRef(A->getValue()).substr(1));
+      return std::string(Buffer);
+    }
+    return A->getValue();
+  };
+
   for (const auto *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.
@@ -3202,16 +3218,7 @@ static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
         IsIndexHeaderMap ? frontend::IndexHeaderMap : frontend::Angled;
 
     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 = std::string(Buffer);
-    }
-
-    Opts.AddPath(Path, Group, IsFramework,
+    Opts.AddPath(PrefixHeaderPath(A, IsFramework), Group, IsFramework,
                  /*IgnoreSysroot*/ true);
     IsIndexHeaderMap = false;
   }
@@ -3229,12 +3236,18 @@ static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
   }
 
   for (const auto *A : Args.filtered(OPT_idirafter))
-    Opts.AddPath(A->getValue(), frontend::After, false, true);
+    Opts.AddPath(PrefixHeaderPath(A), frontend::After, false, true);
   for (const auto *A : Args.filtered(OPT_iquote))
-    Opts.AddPath(A->getValue(), frontend::Quoted, false, true);
-  for (const auto *A : Args.filtered(OPT_isystem, OPT_iwithsysroot))
-    Opts.AddPath(A->getValue(), frontend::System, false,
-                 !A->getOption().matches(OPT_iwithsysroot));
+    Opts.AddPath(PrefixHeaderPath(A), frontend::Quoted, false, true);
+
+  for (const auto *A : Args.filtered(OPT_isystem, OPT_iwithsysroot)) {
+    if (A->getOption().matches(OPT_iwithsysroot)) {
+      Opts.AddPath(A->getValue(), frontend::System, false,
+                   /*IgnoreSysRoot=*/false);
+      continue;
+    }
+    Opts.AddPath(PrefixHeaderPath(A), frontend::System, false, true);
+  }
   for (const auto *A : Args.filtered(OPT_iframework))
     Opts.AddPath(A->getValue(), frontend::System, true, true);
   for (const auto *A : Args.filtered(OPT_iframeworkwithsysroot))