Fallback option for colorized output when terminfo isn't available

Try to detect the terminal color support by checking the value of the
TERM environment variable. This is not great, but it's better than
nothing when terminfo library isn't available, which may still be the
case on some Linux distributions.

Differential Revision: https://reviews.llvm.org/D42055

llvm-svn: 322962

llvm/lib/Support/Unix/Process.inc

@@ -369,6 +369,21 @@ static bool terminalHasColors(int fd) {
   // Return true if we found a color capabilities for the current terminal.
   if (HasColors)
     return true;
+#else
+  // When the terminfo database is not available, check if the current terminal
+  // is one of terminals that are known to support ANSI color escape codes.
+  if (const char *TermStr = std::getenv("TERM")) {
+    return StringSwitch<bool>(TermStr)
+      .Case("ansi", true)
+      .Case("cygwin", true)
+      .Case("linux", true)
+      .StartsWith("screen", true)
+      .StartsWith("xterm", true)
+      .StartsWith("vt100", true)
+      .StartsWith("rxvt", true)
+      .EndsWith("color", true)
+      .Default(false);
+  }
 #endif
 
   // Otherwise, be conservative.