[Driver] Fix implicit config files from prefixed symlinks

[mstorsjo]

Summary

If -no-canonical-prefixes isn't used, the clang executable name used is the one of the actual executable, not the name of the symlink that the user invoked.

In these cases, the target prefix was overridden based on the clang executable name. (On the other hand the implicit -target option that such a symlink adds, is added as an actual command line parameter in tools/driver/driver.cop, before resolving the symlink and finding the actual clang executable.

Use the original ClangNameParts (set from argv[0] in tools/driver/driver.cpp) if it seems to be initialized propery.

All existing tests of this feature used -no-canonical-prefixes (possibly because it also makes the driver look in the directory of the symlink instead of the directory of the executable); add another one that uses --config-user-dir= to specify the directory instead. (For actual users of such symlinks, outisde of the test suite, the directory is probably the same for both.)

This makes this feature work more like what the documentation describes.

[sepavloff]

Thank you for fixing this issue!

LGTM

lib/Driver/Driver.cpp

132 ↗

(On Diff #143560)

Maybe this check could be made a method of ParsedClangName, something like isEmpty?

[mstorsjo]

Added an isEmpty() method.

Btw, did you see https://bugs.llvm.org/show_bug.cgi?id=37196? That one feels quite a bit more convolved so I don't really know (so far) how to approach fixing that.

[sepavloff]

In D45964#1077217, @mstorsjo wrote:

Added an isEmpty() method.

This variant is more readable.

Btw, did you see https://bugs.llvm.org/show_bug.cgi?id=37196? That one feels quite a bit more convolved so I don't really know (so far) how to approach fixing that.

Indeed, that bug looked mysterious. The reason is that InputArgList assumes its field ArgStrings contains strings for each argument exactly in the same order, this condition was broken when arguments from config file and from invocation were merged. I will commit the patch soon.

cfe/trunk/include/clang/Driver/ToolChain.h

struct ParsedClangName {
 
   ParsedClangName() = default;
   ParsedClangName(std::string Suffix, const char *Mode)
       : ModeSuffix(Suffix), DriverMode(Mode) {}
   ParsedClangName(std::string Target, std::string Suffix, const char *Mode,
                   bool IsRegistered)
       : TargetPrefix(Target), ModeSuffix(Suffix), DriverMode(Mode),
         TargetIsValid(IsRegistered) {}
+
+  bool isEmpty() const {
+    return TargetPrefix.empty() && ModeSuffix.empty() && DriverMode == nullptr;
+  }
 };
 
 /// ToolChain - Access to tools for a single platform.
 class ToolChain {
 public:
   using path_list = SmallVector<std::string, 16>;
 
   enum CXXStdlibType {

cfe/trunk/lib/Driver/Driver.cpp

if (ClangResourceDir != "") {
     llvm::sys::path::append(P, Twine("lib") + ClangLibdirSuffix, "clang",
                             CLANG_VERSION_STRING);
   }
   ResourceDir = P.str();
 }
 
 void Driver::ParseDriverMode(StringRef ProgramName,
                              ArrayRef<const char *> Args) {
+  if (ClangNameParts.isEmpty())
     ClangNameParts = ToolChain::getTargetAndModeFromProgramName(ProgramName);
   setDriverModeFromOption(ClangNameParts.DriverMode);
 
   for (const char *ArgPtr : Args) {
     // Ignore nullptrs, they are the response file's EOL markers.
     if (ArgPtr == nullptr)
       continue;
     const StringRef Arg = ArgPtr;
     setDriverModeFromOption(Arg);

cfe/trunk/test/Driver/config-file3.c

 // RUN: echo "-Wundefined-func-template" > %T/testdmode/qqq-clang-g++.cfg
 // RUN: echo "-Werror" > %T/testdmode/qqq.cfg
 // RUN: %T/testdmode/qqq-clang-g++ --config-system-dir= --config-user-dir= -c -no-canonical-prefixes %s -### 2>&1 | FileCheck %s -check-prefix FULL-NAME
 //
 // FULL-NAME: Configuration file: {{.*}}/testdmode/qqq-clang-g++.cfg
 // FULL-NAME: -Wundefined-func-template
 // FULL-NAME-NOT: -Werror
 //
+//--- Invocation qqq-clang-g++ tries to find config file qqq-clang-g++.cfg even without -no-canonical-prefixes.
+// (As the clang executable and symlink are in different directories, this
+// requires specifying the path via --config-*-dir= though.)
+//
+// RUN: %T/testdmode/qqq-clang-g++ --config-system-dir= --config-user-dir=%T/testdmode -c %s -### 2>&1 | FileCheck %s -check-prefix SYMLINK
+//
+// SYMLINK: Configuration file: {{.*}}/testdmode/qqq-clang-g++.cfg
+//
 //--- File specified by --config overrides config inferred from clang executable.
 //
 // RUN: %T/testdmode/qqq-clang-g++ --config-system-dir=%S/Inputs/config --config-user-dir= --config i386-qqq -c -no-canonical-prefixes %s -### 2>&1 | FileCheck %s -check-prefix CHECK-EXPLICIT
 //
 // CHECK-EXPLICIT: Configuration file: {{.*}}/Inputs/config/i386-qqq.cfg
 //
 //--- Invocation qqq-clang-g++ tries to find config file qqq.cfg if qqq-clang-g++.cfg is not found.
 //