StatusPrinter: only strip ANSI sequences when needed.

Just check for the ESC character in the `output` string,
if none is present, or if the terminal supports color,
avoid unnecessary busy work (string allocations and
parsing).

src/status_printer.cc

@@ -216,37 +216,34 @@ void StatusPrinter::BuildEdgeFinished(Edge* edge, int64_t start_time_millis,
     printer_.PrintOnNewLine(edge->EvaluateCommand() + "\n");
   }
 
-  if (!output.empty()) {
-    // ninja sets stdout and stderr of subprocesses to a pipe, to be able to
-    // check if the output is empty. Some compilers, e.g. clang, check
-    // isatty(stderr) to decide if they should print colored output.
-    // To make it possible to use colored output with ninja, subprocesses should
-    // be run with a flag that forces them to always print color escape codes.
-    // To make sure these escape codes don't show up in a file if ninja's output
-    // is piped to a file, ninja strips ansi escape codes again if it's not
-    // writing to a |smart_terminal_|.
-    // (Launching subprocesses in pseudo ttys doesn't work because there are
-    // only a few hundred available on some systems, and ninja can launch
-    // thousands of parallel compile commands.)
-    string final_output;
-    if (!printer_.supports_color())
-      final_output = StripAnsiEscapeCodes(output);
-    else
-      final_output = output;
-
 #ifdef _WIN32
-    // Fix extra CR being added on Windows, writing out CR CR LF (#773)
-    fflush(stdout);  // Begin Windows extra CR fix
-    _setmode(_fileno(stdout), _O_BINARY);
+  // Fix extra CR being added on Windows, writing out CR CR LF (#773)
+  fflush(stdout);  // Begin Windows extra CR fix
+  _setmode(_fileno(stdout), _O_BINARY);
 #endif
 
+  // ninja sets stdout and stderr of subprocesses to a pipe, to be able to
+  // check if the output is empty. Some compilers, e.g. clang, check
+  // isatty(stderr) to decide if they should print colored output.
+  // To make it possible to use colored output with ninja, subprocesses should
+  // be run with a flag that forces them to always print color escape codes.
+  // To make sure these escape codes don't show up in a file if ninja's output
+  // is piped to a file, ninja strips ansi escape codes again if it's not
+  // writing to a |smart_terminal_|.
+  // (Launching subprocesses in pseudo ttys doesn't work because there are
+  // only a few hundred available on some systems, and ninja can launch
+  // thousands of parallel compile commands.)
+  if (printer_.supports_color() || output.find('\x1b') == std::string::npos) {
+    printer_.PrintOnNewLine(output);
+  } else {
+    std::string final_output = StripAnsiEscapeCodes(output);
     printer_.PrintOnNewLine(final_output);
+  }
 
 #ifdef _WIN32
-    fflush(stdout);
-    _setmode(_fileno(stdout), _O_TEXT);  // End Windows extra CR fix
+  fflush(stdout);
+  _setmode(_fileno(stdout), _O_TEXT);  // End Windows extra CR fix
 #endif
-  }
 }
 
 void StatusPrinter::BuildStarted() {