don't leak the build_log file descriptor into subprocesses

Closes issue #74.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/build_log.cc b/src/build_log.cc
index 8c45c77..c3ae1ab 100644
--- a/src/build_log.cc
+++ b/src/build_log.cc
@@ -15,6 +15,7 @@
 #include "build_log.h"
 
 #include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -34,6 +35,21 @@ namespace {
 const char kFileSignature[] = "# ninja log v2\n";
 const int kCurrentVersion = 2;
 
+void SetCloseOnExec(FILE* file) {
+#ifndef _WIN32
+  int flags = fcntl(fileno(file), F_GETFD);
+  if (flags < 0) {
+    perror("fcntl(F_GETFD)");
+  } else {
+    if (fcntl(fileno(file), F_SETFD, flags | FD_CLOEXEC) < 0)
+      perror("fcntl(F_SETFD)");
+  }
+#else
+  // On Windows, handles must be explicitly marked to be passed to a
+  // spawned process, so there's nothing to do here.
+#endif  // WIN32
+}
+
 }
 
 BuildLog::BuildLog()
@@ -55,6 +71,7 @@ bool BuildLog::OpenForWrite(const string& path, string* err) {
     return false;
   }
   setvbuf(log_file_, NULL, _IOLBF, BUFSIZ);
+  SetCloseOnExec(log_file_);
 
   if (ftell(log_file_) == 0) {
     if (fwrite(kFileSignature, sizeof(kFileSignature) - 1, 1, log_file_) < 1) {