[clang-cl] Add support for CL and _CL_ environment variables

[majnemer]

Summary

cl uses 'CL' and '_CL_' to prepend and append command line options to
the given argument vector. There is an additional quirk whereby '#' is
transformed into '='.

[rnk]

lgtm

tools/driver/driver.cpp

464–466 ↗

(On Diff #31640)

How about adjusting all the options in place and then inserting them all at once to avoid the N^2 complexity?

[hans]

Out of curiosity, did you run in to something that relies on this in the wild?

tools/driver/driver.cpp

452 ↗

(On Diff #31640)

Maybe don't take the parameter as a const char* if the constness needs to be dropped for the adjusting to take place? The const_cast could just be moved to where you make the call below.

[rnk]

tools/driver/driver.cpp

451 ↗

(On Diff #31640)

I'd also rather factor this out of driver main, since it's really not important to most readers.

452 ↗

(On Diff #31640)

I think TokenizeCommandLine builds you a list of const strings, unfortunately. We could avoid the cast if we hooked into the tokenization or StringSaver, but it didn't seem worth it.

cfe/trunk/test/Driver/cl-options.c

 // Z7_gdwarf: "-gdwarf-4"
 
 // RUN: %clang_cl -fmsc-version=1800 -TP -### -- %s 2>&1 | FileCheck -check-prefix=CXX11 %s
 // CXX11: -std=c++11
 
 // RUN: %clang_cl -fmsc-version=1900 -TP -### -- %s 2>&1 | FileCheck -check-prefix=CXX14 %s
 // CXX14: -std=c++14
 
+// RUN: env CL="/Gy" %clang_cl -### -- %s 2>&1 | FileCheck -check-prefix=ENV-CL %s
+// ENV-CL: "-ffunction-sections"
+
+// RUN: env CL="/Gy" _CL_="/Gy- -- %s" %clang_cl -### 2>&1 | FileCheck -check-prefix=ENV-_CL_ %s
+// ENV-_CL_-NOT: "-ffunction-sections"
+
 // Accept "core" clang options.
 // (/Zs is for syntax-only, -Werror makes it fail hard on unknown options)
 // RUN: %clang_cl \
 // RUN:     --driver-mode=cl \
 // RUN:     -fcolor-diagnostics \
 // RUN:     -fno-color-diagnostics \
 // RUN:     -fdiagnostics-color \
 // RUN:     -fno-diagnostics-color \

cfe/trunk/tools/driver/driver.cpp

if (llvm::TargetRegistry::lookupTarget(Prefix, IgnoredError)) {
     auto it = ArgVector.begin();
     if (it != ArgVector.end())
       ++it;
     const char *arr[] = { "-target", GetStableCStr(SavedStrings, Prefix) };
     ArgVector.insert(it, std::begin(arr), std::end(arr));
   }
 }
 
+static void getCLEnvVarOptions(std::string &EnvValue, llvm::StringSaver &Saver,
+                               SmallVectorImpl<const char *> &Opts) {
+  llvm::cl::TokenizeWindowsCommandLine(EnvValue, Saver, Opts);
+  // The first instance of '#' should be replaced with '=' in each option.
+  for (const char *Opt : Opts)
+    if (char *NumberSignPtr = const_cast<char *>(::strchr(Opt, '#')))
+      *NumberSignPtr = '=';
+}
+
 static void SetBackdoorDriverOutputsFromEnvVars(Driver &TheDriver) {
   // Handle CC_PRINT_OPTIONS and CC_PRINT_OPTIONS_FILE.
   TheDriver.CCPrintOptions = !!::getenv("CC_PRINT_OPTIONS");
   if (TheDriver.CCPrintOptions)
     TheDriver.CCPrintOptionsFilename = ::getenv("CC_PRINT_OPTIONS_FILE");
 
   // Handle CC_PRINT_HEADERS and CC_PRINT_HEADERS_FILE.
   TheDriver.CCPrintHeaders = !!::getenv("CC_PRINT_HEADERS");
for (int i = 1, size = argv.size(); i < size; ++i) {
     if (argv[i] == nullptr)
       continue;
     if (StringRef(argv[i]) == "-no-canonical-prefixes") {
       CanonicalPrefixes = false;
       break;
     }
   }
 
+  // Handle CL and _CL_ which permits additional command line options to be
+  // prepended or appended.
+  if (Tokenizer == &llvm::cl::TokenizeWindowsCommandLine) {
+    // Arguments in "CL" are prepended.
+    llvm::Optional<std::string> OptCL = llvm::sys::Process::GetEnv("CL");
+    if (OptCL.hasValue()) {
+      SmallVector<const char *, 8> PrependedOpts;
+      getCLEnvVarOptions(OptCL.getValue(), Saver, PrependedOpts);
+
+      // Insert right after the program name to prepend to the argument list.
+      argv.insert(argv.begin() + 1, PrependedOpts.begin(), PrependedOpts.end());
+    }
+    // Arguments in "_CL_" are appended.
+    llvm::Optional<std::string> Opt_CL_ = llvm::sys::Process::GetEnv("_CL_");
+    if (Opt_CL_.hasValue()) {
+      SmallVector<const char *, 8> AppendedOpts;
+      getCLEnvVarOptions(Opt_CL_.getValue(), Saver, AppendedOpts);
+
+      // Insert at the end of the argument list to append.
+      argv.append(AppendedOpts.begin(), AppendedOpts.end());
+    }
+  }
+
   std::set<std::string> SavedStrings;
   // Handle CCC_OVERRIDE_OPTIONS, used for editing a command line behind the
   // scenes.
   if (const char *OverrideStr = ::getenv("CCC_OVERRIDE_OPTIONS")) {
     // FIXME: Driver shouldn't take extra initial argument.
     ApplyQAOverride(argv, OverrideStr, SavedStrings);
   }