Driver: Add a --working-directory option which can be used to cause the compiler

to operate "as if" in a certain working directory.
 - For now, we just implement this by changing the actual working directory, but
   eventually we would want to handle this transparently. This is useful to
   avoid an extra exec() pair in some situations, and will be something we would
   want to support for more flexibility in using the Clang libraries.

llvm-svn: 140409

3 files changed, 16 insertions, 0 deletions

diff --git a/clang/docs/tools/clang.pod b/clang/docs/tools/clang.pod
index 704cc8743ba..abecd1c8ef5 100644
--- a/clang/docs/tools/clang.pod
+++ b/clang/docs/tools/clang.pod
@@ -407,6 +407,13 @@ Print timing summary of each stage of compilation.
 
 Show commands to run and use verbose output.
 
+=item B<--working-directory>
+
+Use the given argument as the effective working directory to run the compiler
+in. This is useful for running the compiler as if in a specific working
+directory without the overhead of having to change directory using an auxiliary
+process.
+
 =back
 
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 3f48b96d758..770b7d86f9f 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -855,6 +855,8 @@ def _verbose : Flag<"--verbose">, Alias<v>;
 def _version : Flag<"--version">;
 def _warn__EQ : Joined<"--warn-=">, Alias<W_Joined>;
 def _warn_ : Joined<"--warn-">, Alias<W_Joined>;
+def _working_directory : Separate<"--working-directory">,
+    HelpText<"Use the given argument as the effective working directory">;
 def _write_dependencies : Flag<"--write-dependencies">, Alias<MD>;
 def _write_user_dependencies : Flag<"--write-user-dependencies">, Alias<MMD>;
 def _ : Joined<"--">, Flags<[Unsupported]>;
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index ec9295d6fb7..d64eab5999b 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -323,6 +323,13 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
   if (Args->hasArg(options::OPT_nostdlib))
     UseStdLib = false;
 
+  // Honor --working-directory. Eventually we want to handle this completely
+  // internally to support good use as a library, but for now we just change our
+  // working directory.
+  if (const Arg *A = Args->getLastArg(options::OPT__working_directory)) {
+    ::chdir(A->getValue(*Args));
+  }
+
   Host = GetHostInfo(DefaultHostTriple.c_str());
 
   // Perform the default argument translations.