Strip ansi escape sequences from subcommand output when not writing to a smart terminal.

1 files changed, 20 insertions, 2 deletions

diff --git a/src/build.cc b/src/build.cc
index 94c9d77..8d0abce 100644
--- a/src/build.cc
+++ b/src/build.cc
@@ -133,8 +133,26 @@ void BuildStatus::BuildEdgeFinished(Edge* edge,
     if (!success)
       printf("FAILED: %s\n", edge->EvaluateCommand().c_str());
 
-    if (!output.empty())
-      printf("%s", output.c_str());
+    // 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.)
+    // TODO: There should be a flag to disable escape code stripping.
+    string final_output;
+    if (!smart_terminal_)
+      final_output = StripAnsiEscapeCodes(output);
+    else
+      final_output = output;
+
+    if (!final_output.empty())
+      printf("%s", final_output.c_str());
   }
 }