Refactor the code in clang to find a file in a PATH like environment variable into a helper function

[hans]

The code itself looks good, but I'm not sure this is the right place.

include/llvm/Support/Program.h

156 ↗

(On Diff #10597)

I'm not sure Program.h is the right place. This header seems mostly concerned with running programs.

Perhaps Process.h, next to GetEnv() is a better place? Or maybe FileSystem.h?

[• ehsan]

I chose Program.h because I found FindProgramByName there... But I'm not sure if that's the best place either. Can you please suggest either Process.h or FileSystem.h? Either would work for me. :-)

[hans]

I chose Program.h because I found FindProgramByName there... But I'm not sure if that's the best place either. Can you please suggest either Process.h or FileSystem.h? Either would work for me. :-)

I feel this is tightly related to GetEnv, so let's go for Process.

[• ehsan]

Moved the function to Process.h.

[hans]

lgtm

lib/Support/Process.cpp

74

Nit: The curly should go on the previous line.

77

I guess we can drop hasValue() here since Optional has its bool operator.

[• ehsan]

Landed in r212057.

include/llvm/Support/Process.h

public:
   /// occur when a program fails.
   /// @brief Prevent core file generation.
   static void PreventCoreFiles();
 
   // This function returns the environment variable \arg name's value as a UTF-8
   // string. \arg Name is assumed to be in UTF-8 encoding too.
   static Optional<std::string> GetEnv(StringRef name);
 
+  /// This function searches for an existing file in the list of directories
+  /// in a PATH like environment variable, and returns the first file found,
+  /// according to the order of the entries in the PATH like environment
+  /// variable.
+  static Optional<std::string> FindInEnvPath(const std::string& EnvName,
+                                             const std::string& FileName);
+
   /// This function returns a SmallVector containing the arguments passed from
   /// the operating system to the program.  This function expects to be handed
   /// the vector passed in from main.
   static std::error_code
   GetArgumentVector(SmallVectorImpl<const char *> &Args,
                     ArrayRef<const char *> ArgsFromMain,
                     SpecificBumpPtrAllocator<char> &ArgAllocator);
 

lib/Support/Process.cpp

 //===-- Process.cpp - Implement OS Process Concept --------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 //  This header file implements the operating system Process concept.
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Support/Program.h"
 
 using namespace llvm;
 using namespace sys;
 
 //===----------------------------------------------------------------------===//
 //=== WARNING: Implementation here must contain only TRULY operating system
 //===          independent code.
 //===----------------------------------------------------------------------===//

 static volatile TimeValue DummyTimeValue = getElapsedWallTime();
 
 // Implement this routine by using the static helpers above. They're already
 // portable.
 TimeValue self_process::get_wall_time() const {
   return getElapsedWallTime();
 }
 
+Optional<std::string> Process::FindInEnvPath(const std::string& EnvName,
+                                             const std::string& FileName)
+{
+  Optional<std::string> FoundPath;
+  Optional<std::string> OptPath = Process::GetEnv(EnvName);
+  if (!OptPath.hasValue())
+    return FoundPath;
+
+  const char EnvPathSeparatorStr[] = {EnvPathSeparator, '\0'};
+  SmallVector<StringRef, 8> Dirs;
+  SplitString(OptPath.getValue(), Dirs, EnvPathSeparatorStr);
+
+  for (const auto &Dir : Dirs) {
+    if (Dir.empty())
+      continue;
+
+    SmallString<128> FilePath(Dir);
+    path::append(FilePath, FileName);
+    if (fs::exists(Twine(FilePath))) {
+      FoundPath = FilePath.str();
+      break;
+    }
+  }
+
+  return FoundPath;
+}
+
 
 #define COLOR(FGBG, CODE, BOLD) "\033[0;" BOLD FGBG CODE "m"
 
 #define ALLCOLORS(FGBG,BOLD) {\
     COLOR(FGBG, "0", BOLD),\
     COLOR(FGBG, "1", BOLD),\
     COLOR(FGBG, "2", BOLD),\
     COLOR(FGBG, "3", BOLD),\