diff --git a/CMakeLists.txt b/CMakeLists.txt
index d73ce893..86125809 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,7 +24,7 @@ add_executable(ccls "")
 #   debug: -g
 #   release: -O3 -DNDEBUG
 
-# Enable C++14 (Required)
+# Enable C++17 (Required)
 set_property(TARGET ccls PROPERTY CXX_STANDARD 17)
 set_property(TARGET ccls PROPERTY CXX_STANDARD_REQUIRED ON)
 # Disable gnu extensions except for Cygwin which needs them to build properly
diff --git a/src/fuzzy_match.cc b/src/fuzzy_match.cc
index c72e958c..182680ae 100644
--- a/src/fuzzy_match.cc
+++ b/src/fuzzy_match.cc
@@ -46,7 +46,9 @@ void CalculateRoles(std::string_view s, int roles[], int* class_set) {
 }  // namespace
 
 int FuzzyMatcher::MissScore(int j, bool last) {
-  int s = last ? -10 : 0;
+  int s = -3;
+  if (last)
+    s -= 10;
   if (text_role[j] == Head)
     s -= 10;
   return s;
@@ -54,8 +56,10 @@ int FuzzyMatcher::MissScore(int j, bool last) {
 
 int FuzzyMatcher::MatchScore(int i, int j, bool last) {
   int s = 0;
+  // Case matching.
   if (pat[i] == text[j]) {
     s++;
+    // pat contains uppercase letters or prefix matching.
     if ((pat_set & 1 << Upper) || i == j)
       s++;
   }
@@ -65,8 +69,10 @@ int FuzzyMatcher::MatchScore(int i, int j, bool last) {
     else if (text_role[j] == Tail)
       s -= 10;
   }
+  // Matching a tail while previous char wasn't matched.
   if (text_role[j] == Tail && i && !last)
     s -= 30;
+  // First char of pat matches a tail.
   if (i == 0 && text_role[j] == Tail)
     s -= 40;
   return s;
@@ -119,7 +125,7 @@ int FuzzyMatcher::Match(std::string_view text) {
   // character has a penulty.
   int ret = kMinScore;
   for (int j = pat.size(); j <= n; j++)
-    ret = std::max(ret, dp[pat.size() & 1][j][1] - 3 * (n - j));
+    ret = std::max(ret, dp[pat.size() & 1][j][1] - 2 * (n - j));
   return ret;
 }
 
diff --git a/src/platform_posix.cc b/src/platform_posix.cc
index b03ec4b7..d41cee68 100644
--- a/src/platform_posix.cc
+++ b/src/platform_posix.cc
@@ -284,9 +284,12 @@ void TraceMe() {
 std::string GetExternalCommandOutput(const std::vector<std::string>& command,
                                      std::string_view input) {
   int pin[2], pout[2];
-  if (pipe(pin) < 0)
+  if (pipe(pin) < 0) {
+    perror("pipe(stdin)");
     return "";
+  }
   if (pipe(pout) < 0) {
+    perror("pipe(stdout)");
     close(pin[0]);
     close(pin[1]);
     return "";
@@ -316,6 +319,7 @@ std::string GetExternalCommandOutput(const std::vector<std::string>& command,
   ssize_t n;
   while ((n = read(pin[0], buf, sizeof buf)) > 0)
     ret.append(buf, n);
+  close(pin[0]);
   waitpid(child, NULL, 0);
   return ret;
 }