cmDependsCompiler: rely now on cmGccDepfileReader for depfile parser

To avoid duplicate effort of depfile parsing and enhance robustness
of parsing against mal-formed depfiles in preparation of DEPFILE option
support of add_custom_command command for makefiles generators.

Source/cmDependsCompiler.cxx

@@ -5,10 +5,12 @@
 
 #include <algorithm>
 #include <map>
+#include <memory>
 #include <string>
 #include <unordered_set>
 #include <utility>
 
+#include <cm/optional>
 #include <cm/string_view>
 #include <cm/vector>
 #include <cmext/string_view>
@@ -16,77 +18,12 @@
 #include "cmsys/FStream.hxx"
 
 #include "cmFileTime.h"
+#include "cmGccDepfileReader.h"
 #include "cmGlobalUnixMakefileGenerator3.h"
 #include "cmLocalUnixMakefileGenerator3.h"
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
 
-namespace {
-std::string& ReplaceAll(std::string& data, const std::string& toSearch,
-                        const std::string& replaceStr)
-{
-  // Get the first occurrence
-  auto pos = data.find(toSearch);
-  // Repeat until the end is reached
-  while (pos != std::string::npos) {
-    // Replace this occurrence of Sub String
-    data.replace(pos, toSearch.size(), replaceStr);
-    // Get the next occurrence from the current position
-    pos = data.find(toSearch, pos + replaceStr.size());
-  }
-
-  return data;
-}
-
-std::string& NormalizePath(std::string& item)
-{
-  ReplaceAll(item, "$$", "$");
-  ReplaceAll(item, "\\ ", " ");
-  ReplaceAll(item, "\\#", "#");
-  ReplaceAll(item, "\\", "/");
-
-  return item;
-}
-
-void ParseLine(const std::string& line, std::vector<std::string>& depends)
-{
-  auto start = line.find_first_not_of(' ');
-  if (start == std::string::npos || line[start] == '#') {
-    return;
-  }
-
-  auto index = start;
-  while ((index = line.find(' ', index)) != std::string::npos) {
-    if (line[index - 1] == '\\') {
-      index += 1;
-      continue;
-    }
-
-    auto item = line.substr(start, index - start);
-    if (item.back() != ':') {
-      // check that ':' is not present after some spaces
-      auto index2 = line.find_first_not_of(' ', index + 1);
-      if (index2 == std::string::npos || line[index2] != ':') {
-        // this is a dependency, add it
-        depends.emplace_back(std::move(NormalizePath(item)));
-      } else {
-        index = index2;
-      }
-    }
-
-    start = line.find_first_not_of(' ', index + 1);
-    index = start;
-  }
-  if (start != std::string::npos) {
-    auto item = line.substr(start);
-    if (line.back() != ':') {
-      // this is a dependency, add it
-      depends.emplace_back(std::move(NormalizePath(item)));
-    }
-  }
-}
-}
-
 bool cmDependsCompiler::CheckDependencies(
   const std::string& internalDepFile, const std::vector<std::string>& depFiles,
   cmDepends::DependencyMap& dependencies,
@@ -156,14 +93,15 @@ bool cmDependsCompiler::CheckDependencies(
                                        "\" is newer than depends file \"",
                                        internalDepFile, "\".\n"));
       }
-      cmsys::ifstream fin(depFile.c_str());
-      if (!fin) {
-        continue;
-      }
 
       std::vector<std::string> depends;
-      std::string line;
       if (format == "msvc"_s) {
+        cmsys::ifstream fin(depFile.c_str());
+        if (!fin) {
+          continue;
+        }
+
+        std::string line;
         if (!isValidPath) {
           // insert source as first dependency
           depends.push_back(source);
@@ -172,16 +110,13 @@ bool cmDependsCompiler::CheckDependencies(
           depends.emplace_back(std::move(line));
         }
       } else {
-        while (cmSystemTools::GetLineFromStream(fin, line)) {
+        auto deps = cmReadGccDepfile(depFile.c_str());
-          if (line.empty()) {
+        if (!deps) {
-            continue;
+          continue;
-          }
-          if (line.back() == '\\') {
-            line.pop_back();
-          }
-          ParseLine(line, depends);
         }
 
+        // dependencies generated by the compiler contains only one target
+        depends = std::move(deps->front().paths);
         if (depends.empty()) {
           // unexpectedly empty, ignore it and continue
           continue;