[clang] [Driver] Do not transform explicit --config filename

[mgorny]

Summary

Disable transformations (e.g. attempting to replace target architecture)
in the config filename that is passed explicitly via --config. This
behavior is surprising and confusing -- if user passes an explicit
config filename, Clang should use it as is. The transformations are
still applied when the name is deduced from filename.

Update the tests accordingly. This primarily ensures that full filename
with .cfg suffix is passed to --config (appending .cfg implicitly is
not documented, and would collide with use of filenames with other
suffixes). The config-file2.c suite is removed entirely as it tested
the transformations on the argument to --config. However, the aspects
of that that were not tested as part of config-file3.c are now added
there (based on config filename deduced from executable).

This change streamlines the code in Driver::loadConfigFile(), opening
the possibility of further changes, including support for handling
multiple --config options and refactoring of filename deduction.

[MaskRay]

Thanks!

[sepavloff]

LGTM.

Thanks!

clang/lib/Driver/Driver.cpp

bool Driver::readConfigFile(StringRef FileName) {
   // does not warn on any that is unused.
   for (Arg *A : *CfgOptions)
     A->claim();
   return false;
 }
 
 bool Driver::loadConfigFile() {
   std::string CfgFileName;
-  bool FileSpecifiedExplicitly = false;
 
   // Process options that change search path for config files.
   if (CLOptions) {
     if (CLOptions->hasArg(options::OPT_config_system_dir_EQ)) {
       SmallString<128> CfgDir;
       CfgDir.append(
           CLOptions->getLastArgValue(options::OPT_config_system_dir_EQ));
       if (CfgDir.empty() || getVFS().makeAbsolute(CfgDir))
         SystemConfigDir.clear();
       else
         SystemConfigDir = static_cast<std::string>(CfgDir);
     }
     if (CLOptions->hasArg(options::OPT_config_user_dir_EQ)) {
       SmallString<128> CfgDir;
       CfgDir.append(
           CLOptions->getLastArgValue(options::OPT_config_user_dir_EQ));
       if (CfgDir.empty() || getVFS().makeAbsolute(CfgDir))
         UserConfigDir.clear();
       else
         UserConfigDir = static_cast<std::string>(CfgDir);
     }
   }
 
+  // Prepare list of directories where config file is searched for.
+  StringRef CfgFileSearchDirs[] = {UserConfigDir, SystemConfigDir, Dir};
+
   // First try to find config file specified in command line.
+  llvm::SmallString<128> CfgFilePath;
   if (CLOptions) {
     std::vector<std::string> ConfigFiles =
         CLOptions->getAllArgValues(options::OPT_config);
     if (ConfigFiles.size() > 1) {
       if (!llvm::all_equal(ConfigFiles)) {
         Diag(diag::err_drv_duplicate_config);
         return true;
       }
if (!ConfigFiles.empty()) {
               Status->getType() != llvm::sys::fs::file_type::regular_file) {
             Diag(diag::err_drv_config_file_not_exist) << CfgFilePath;
             return true;
           }
         }
         return readConfigFile(CfgFilePath);
       }
 
-      FileSpecifiedExplicitly = true;
+      // Look for the configuration file in the usual locations.
+      if (searchForFile(CfgFilePath, CfgFileSearchDirs, CfgFileName, getVFS()))
+        return readConfigFile(CfgFilePath);
+
+      // Report error but only if config file was specified explicitly, by
+      // option --config. If it was deduced from executable name, it is not an
+      // error.
+      Diag(diag::err_drv_config_file_not_found) << CfgFileName;
+      for (const StringRef &SearchDir : CfgFileSearchDirs)
+        if (!SearchDir.empty())
+          Diag(diag::note_drv_config_file_searched_in) << SearchDir;
+      return true;
     }
   }
 
   if (!(CLOptions && CLOptions->hasArg(options::OPT_no_default_config))) {
     // If config file is not specified explicitly, try to deduce configuration
     // from executable name. For instance, an executable 'armv7l-clang' will
     // search for config file 'armv7l-clang.cfg'.
     if (CfgFileName.empty() && !ClangNameParts.TargetPrefix.empty())
bool Driver::loadConfigFile() {
   // redefine architecture (with options like -m32 -LE etc), try finding new
   // config file with that architecture.
   SmallString<128> FixedConfigFile;
   size_t FixedArchPrefixLen = 0;
   if (ArchPrefixLen) {
     // Get architecture name from config file name like 'i386.cfg' or
     // 'armv7l-clang.cfg'.
     // Check if command line options changes effective triple.
-    llvm::Triple EffectiveTriple = computeTargetTriple(*this,
-                                             CfgTriple.getTriple(), *CLOptions);
+    llvm::Triple EffectiveTriple =
+        computeTargetTriple(*this, CfgTriple.getTriple(), *CLOptions);
     if (CfgTriple.getArch() != EffectiveTriple.getArch()) {
       FixedConfigFile = EffectiveTriple.getArchName();
       FixedArchPrefixLen = FixedConfigFile.size();
       // Append the rest of original file name so that file name transforms
       // like: i386-clang.cfg -> x86_64-clang.cfg.
       if (ArchPrefixLen < CfgFileName.size())
         FixedConfigFile += CfgFileName.substr(ArchPrefixLen);
     }
   }
 
-  // Prepare list of directories where config file is searched for.
-  StringRef CfgFileSearchDirs[] = {UserConfigDir, SystemConfigDir, Dir};
-
   // Try to find config file. First try file with corrected architecture.
-  llvm::SmallString<128> CfgFilePath;
   if (!FixedConfigFile.empty()) {
     if (searchForFile(CfgFilePath, CfgFileSearchDirs, FixedConfigFile,
                       getVFS()))
       return readConfigFile(CfgFilePath);
     // If 'x86_64-clang.cfg' was not found, try 'x86_64.cfg'.
     FixedConfigFile.resize(FixedArchPrefixLen);
     FixedConfigFile.append(".cfg");
     if (searchForFile(CfgFilePath, CfgFileSearchDirs, FixedConfigFile,
bool Driver::loadConfigFile() {
   if (!ClangNameParts.ModeSuffix.empty() &&
       !ClangNameParts.TargetPrefix.empty()) {
     CfgFileName.assign(ClangNameParts.TargetPrefix);
     CfgFileName.append(".cfg");
     if (searchForFile(CfgFilePath, CfgFileSearchDirs, CfgFileName, getVFS()))
       return readConfigFile(CfgFilePath);
   }
 
-  // Report error but only if config file was specified explicitly, by option
-  // --config. If it was deduced from executable name, it is not an error.
-  if (FileSpecifiedExplicitly) {
-    Diag(diag::err_drv_config_file_not_found) << CfgFileName;
-    for (const StringRef &SearchDir : CfgFileSearchDirs)
-      if (!SearchDir.empty())
-        Diag(diag::note_drv_config_file_searched_in) << SearchDir;
-    return true;
-  }
-
+  // If we were unable to find a config file deduced from executable name,
+  // do not report an error.
   return false;
 }
 
 Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
   llvm::PrettyStackTraceString CrashInfo("Compilation construction");
 
   // FIXME: Handle environment options which affect driver behavior, somewhere
   // (client?). GCC_EXEC_PREFIX, LPATH, CC_PRINT_OPTIONS.

clang/test/Driver/config-file-errs.c

 //--- Argument of '--config' must be existing file, if it is specified by path.
 //
 // RUN: not %clang --config somewhere/nonexistent-config-file 2>&1 | FileCheck %s -check-prefix CHECK-NONEXISTENT
 // CHECK-NONEXISTENT: configuration file '{{.*}}somewhere/nonexistent-config-file' does not exist
 
 
 //--- Argument of '--config' must exist somewhere in well-known directories, if it is specified by bare name.
 //
-// RUN: not %clang --config-system-dir= --config-user-dir= --config nonexistent-config-file 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND0
+// RUN: not %clang --config-system-dir= --config-user-dir= --config nonexistent-config-file.cfg 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND0
 // CHECK-NOTFOUND0: configuration file 'nonexistent-config-file.cfg' cannot be found
 // CHECK-NOTFOUND0-NEXT: was searched for in the directory:
 // CHECK-NOTFOUND0-NOT: was searched for in the directory:
 //
-// RUN: not %clang --config-system-dir= --config-user-dir=%S/Inputs/config2 --config nonexistent-config-file 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND1
+// RUN: not %clang --config-system-dir= --config-user-dir=%S/Inputs/config2 --config nonexistent-config-file.cfg 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND1
 // CHECK-NOTFOUND1: configuration file 'nonexistent-config-file.cfg' cannot be found
 // CHECK-NOTFOUND1-NEXT: was searched for in the directory: {{.*}}/Inputs/config2
 // CHECK-NOTFOUND1-NEXT: was searched for in the directory:
 // CHECK-NOTFOUND1-NOT: was searched for in the directory:
 //
-// RUN: not %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config nonexistent-config-file 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND2
+// RUN: not %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config nonexistent-config-file.cfg 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND2
 // CHECK-NOTFOUND2: configuration file 'nonexistent-config-file.cfg' cannot be found
 // CHECK-NOTFOUND2-NEXT: was searched for in the directory: {{.*}}/Inputs/config
 // CHECK-NOTFOUND2-NEXT: was searched for in the directory:
 // CHECK-NOTFOUND2-NOT: was searched for in the directory:
 //
-// RUN: not %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config nonexistent-config-file 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND3
+// RUN: not %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config nonexistent-config-file.cfg 2>&1 | FileCheck %s -check-prefix CHECK-NOTFOUND3
 // CHECK-NOTFOUND3: configuration file 'nonexistent-config-file.cfg' cannot be found
 // CHECK-NOTFOUND3-NEXT: was searched for in the directory: {{.*}}/Inputs/config2
 // CHECK-NOTFOUND3-NEXT: was searched for in the directory: {{.*}}/Inputs/config
 // CHECK-NOTFOUND3-NEXT: was searched for in the directory:
 
 
 //--- Argument in config file cannot cross the file boundary
 //
 // RUN: not %clang --config %S/Inputs/config-5.cfg x86_64-unknown-linux-gnu -c %s 2>&1 | FileCheck %s -check-prefix CHECK-CROSS
 // CHECK-CROSS: error: argument to '-target' is missing

clang/test/Driver/config-file.c

 //
 // RUN: %clang --config %S/Inputs/config-4.cfg -S %s -o /dev/null -v 2>&1 | FileCheck %s -check-prefix CHECK-UNUSED
 // CHECK-UNUSED-NOT: argument unused during compilation:
 // CHECK-UNUSED-NOT: 'linker' input unused
 
 
 //--- User directory is searched first.
 //
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config config-4 -S %s -o /dev/null -v 2>&1 | FileCheck %s -check-prefix CHECK-PRECEDENCE
+// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config config-4.cfg -S %s -o /dev/null -v 2>&1 | FileCheck %s -check-prefix CHECK-PRECEDENCE
 // CHECK-PRECEDENCE: Configuration file: {{.*}}Inputs{{.}}config2{{.}}config-4.cfg
 // CHECK-PRECEDENCE: -Wall
 
 
 //--- Duplicate --config options are allowed if the value is the same
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config config-4 --config config-4 -S %s -o /dev/null -v 2>&1 | FileCheck %s -check-prefix CHECK-SAME-CONFIG
+// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config config-4.cfg --config config-4.cfg -S %s -o /dev/null -v 2>&1 | FileCheck %s -check-prefix CHECK-SAME-CONFIG
 // CHECK-SAME-CONFIG: Configuration file: {{.*}}Inputs{{.}}config2{{.}}config-4.cfg

clang/test/Driver/config-file2.c

-// REQUIRES: x86-registered-target
-
-//--- Invocation `clang --config x86_64-qqq -m32` loads `i386-qqq.cfg` if the latter exists.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config x86_64-qqq -m32 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD
-// CHECK-RELOAD: Target: i386
-// CHECK-RELOAD: Configuration file: {{.*}}Inputs{{.}}config{{.}}i386-qqq.cfg
-
-
-//--- Invocation `clang --config x86_64-qqq2 -m32` loads `i386.cfg` if the latter exists in another search directory.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir=%S/Inputs/config2 --config x86_64-qqq2 -m32 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1
-// CHECK-RELOAD1: Target: i386
-// CHECK-RELOAD1: Configuration file: {{.*}}Inputs{{.}}config2{{.}}i386.cfg
-
-
-//--- Invocation `clang --config x86_64-qqq2 -m32` loads `x86_64-qqq2.cfg` if `i386-qqq2.cfg` and `i386.cfg` do not exist.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config x86_64-qqq2 -m32 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD2
-// note: target is overridden due to -m32
-// CHECK-RELOAD2: Target: i386
-// CHECK-RELOAD2: Configuration file: {{.*}}Inputs{{.}}config{{.}}x86_64-qqq2.cfg
-
-
-//--- Invocation `clang --config i386-qqq3 -m64` loads `x86_64.cfg` if `x86_64-qqq3.cfg` does not exist.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config i386-qqq3 -m64 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD3
-// CHECK-RELOAD3: Target: x86_64
-// CHECK-RELOAD3: Configuration file: {{.*}}Inputs{{.}}config{{.}}x86_64.cfg
-
-
-//--- Invocation `clang --config x86_64-qqq -target i386` loads `i386-qqq.cfg` if the latter exists.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config x86_64-qqq -target i386 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD4
-// CHECK-RELOAD4: Target: i386
-// CHECK-RELOAD4: Configuration file: {{.*}}Inputs{{.}}config{{.}}i386-qqq.cfg
-
-
-//--- Invocation `clang --config x86_64-qqq2 -target i386` loads `x86_64-qqq2.cfg` if `i386-qqq2.cfg` and `i386.cfg` do not exist.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config x86_64-qqq2 -target i386 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD5
-// note: target is overridden due to -target i386
-// CHECK-RELOAD5: Target: i386
-// CHECK-RELOAD5: Configuration file: {{.*}}Inputs{{.}}config{{.}}x86_64-qqq2.cfg
-
-
-//--- Invocation `clang --config x86_64-qqq -target i386 -m64` loads `x86_64-qqq.cfg`.
-//
-// RUN: %clang --config-system-dir=%S/Inputs/config --config-user-dir= --config x86_64-qqq -target i386 -m64 -c %s -### 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD6
-// CHECK-RELOAD6: Target: x86_64
-// CHECK-RELOAD6: Configuration file: {{.*}}Inputs{{.}}config{{.}}x86_64-qqq.cfg

clang/test/Driver/config-file3.c

 // 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
+// RUN: %t/testdmode/qqq-clang-g++ --config-system-dir=%S/Inputs/config --config-user-dir= --config i386-qqq.cfg -c -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-EXPLICIT
 //
 // CHECK-EXPLICIT: Configuration file: {{.*}}/Inputs/config/i386-qqq.cfg
 
 //--- --no-default-config disables config search.
 //
 // RUN: %t/testdmode/qqq-clang-g++ --config-system-dir= --config-user-dir=%t/testdmode --no-default-config -c -### %s 2>&1 | FileCheck %s -check-prefix NO-DEFAULT-CONFIG
 //
 // NO-DEFAULT-CONFIG-NOT: Configuration file:

 //    reloading config file.
 
 //--- When reloading config file, x86_64-clang-g++ tries to find config i386-clang-g++.cfg first.
 //
 // RUN: mkdir %t/testreload
 // RUN: ln -s %clang %t/testreload/x86_64-clang-g++
 // RUN: echo "-Wundefined-func-template" > %t/testreload/i386-clang-g++.cfg
 // RUN: echo "-Werror" > %t/testreload/i386.cfg
+// RUN: echo "-Wall" > %t/testreload/x86_64-clang-g++.cfg
 // RUN: %t/testreload/x86_64-clang-g++ --config-system-dir= --config-user-dir= -c -m32 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD
 //
 // CHECK-RELOAD: Configuration file: {{.*}}/testreload/i386-clang-g++.cfg
 // CHECK-RELOAD: -Wundefined-func-template
 // CHECK-RELOAD-NOT: -Werror
+// CHECK-RELOAD-NOT: -Wall
 
-//--- If config file is specified by --config and its name does not start with architecture, it is used without reloading.
-//
-// RUN: %t/testreload/x86_64-clang-g++ --config-system-dir=%S/Inputs --config-user-dir= --config config-3 -c -m32 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1a
-//
-// CHECK-RELOAD1a: Configuration file: {{.*}}/Inputs/config-3.cfg
-//
-// RUN: %t/testreload/x86_64-clang-g++ --config-system-dir=%S/Inputs --config-user-dir= --config config-3 -c --target=i386 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1b
-//
-// CHECK-RELOAD1b: Configuration file: {{.*}}/Inputs/config-3.cfg
+//--- Same for -target in place of -m32.
+// RUN: %t/testreload/x86_64-clang-g++ --config-system-dir= --config-user-dir= -c -target i386 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD
 
-//--- If config file is specified by --config and its name starts with architecture, it is reloaded.
-//
-// RUN: %t/testreload/x86_64-clang-g++ --config-system-dir=%S/Inputs/config --config-user-dir= --config x86_64-qqq -c -m32 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1c
+//--- `-target i386 -m64` should load the 64-bit config.
+// RUN: %t/testreload/x86_64-clang-g++ --config-system-dir= --config-user-dir= -c -target i386 -m64 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1a
 //
-// CHECK-RELOAD1c: Configuration file: {{.*}}/Inputs/config/i386-qqq.cfg
+// CHECK-RELOAD1a: Configuration file: {{.*}}/testreload/x86_64-clang-g++.cfg
+// CHECK-RELOAD1a: -Wall
+// CHECK-RELOAD1a-NOT: -Werror
+// CHECK-RELOAD1a-NOT: -Wundefined-func-template
 
 //--- x86_64-clang-g++ tries to find config i386.cfg if i386-clang-g++.cfg is not found.
 //
 // RUN: rm %t/testreload/i386-clang-g++.cfg
 // RUN: %t/testreload/x86_64-clang-g++ --config-system-dir= --config-user-dir= -c -m32 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1d
 //
 // CHECK-RELOAD1d: Configuration file: {{.*}}/testreload/i386.cfg
 // CHECK-RELOAD1d: -Werror
 // CHECK-RELOAD1d-NOT: -Wundefined-func-template
+// CHECK-RELOAD1d-NOT: -Wall
 
+//--- x86_64-clang-g++ uses x86_64-clang-g++.cfg if i386*.cfg are not found.
+//
+// RUN: rm %t/testreload/i386.cfg
+// RUN: %t/testreload/x86_64-clang-g++ --config-system-dir= --config-user-dir= -c -m32 -no-canonical-prefixes -### %s 2>&1 | FileCheck %s -check-prefix CHECK-RELOAD1a