Add llvm::sys::path::canonical(), which provides the canonicalized

name of a path, after resolving symbolic links and eliminating excess
path elements such as "foo/../" and "./".

This routine still needs a Windows implementation, but I don't have a
Windows machine available. Help? Please?


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125228 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/PathV2.h

@@ -244,6 +244,15 @@ const StringRef filename(StringRef path);
 /// @result The stem of \a path.
 const StringRef stem(StringRef path);
 
+/// Convert path to a canonical form, resolving symbolic links and removing
+/// unnecessary path elements (e.g., "foo/../", "./"). 
+///
+/// @param path A path that is going to be canonicalized by resolving symlinks
+/// and removing unnecessary path elements (e.g., "./").
+///
+/// @param buffer The resulting canonical path.
+void canonical(const char *path, SmallVectorImpl<char> &result);
+  
 /// @brief Get extension.
 ///
 /// If filename contains a dot but not solely one or two dots, result is the

lib/Support/Unix/PathV2.inc

@@ -503,5 +503,35 @@ error_code get_magic(const Twine &path, uint32_t len,
 }
 
 } // end namespace fs
+
+namespace path {
+
+void canonical(const char *path, SmallVectorImpl<char> &buffer) {
+  buffer.resize(PATH_MAX);
+  char *result = realpath(path, buffer.data());
+  if (result) {
+    buffer.resize(strlen(result));
+    return;
+  }
+
+  // A common extension is to support memory allocation of the result when
+  // passing NULL as the second argument.
+  result = realpath(path, 0);
+  if (result) {
+    size_t length = strlen(result);
+    buffer.resize(length);
+    memcpy(buffer.data(), result, length);
+    free(result);
+    return buffer.data();
+  }
+
+  size_t length = strlen(path);
+  buffer.resize(length);
+  memcpy(buffer.data(), path, length);
+  return path;
+}
+
+} // end namespace path
+
 } // end namespace sys
 } // end namespace llvm