From 4fdb9580fedac9669508bef0837f46f1e9310e24 Mon Sep 17 00:00:00 2001
From: Joel Rosdahl <joel@rosdahl.net>
Date: Mon, 17 Aug 2015 21:01:35 +0200
Subject: [PATCH] Wait for compiler subprocess to exit before exiting from a
 signal

This should fix a race condition (albeit a quite unlikely one) related
to removal of the compiler output file(s).
---
 NEWS.txt  |  4 ++++
 ccache.c  | 13 +++++++++++--
 ccache.h  |  2 +-
 execute.c | 12 ++++++------
 4 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/NEWS.txt b/NEWS.txt
index 2776836f8..257d71b9f 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -14,6 +14,10 @@ Bug fixes
 - Made conversion-to-bool explicit to avoid build warnings (and potential
   runtime errors) on legacy systems.
 
+- Wait for compiler subprocess (if any) to exit before exiting from a signal.
+  This should fix a race condition (albeit a quite unlikely one) related to
+  removal of the compiler output file(s).
+
 
 ccache 3.2.3
 ------------
diff --git a/ccache.c b/ccache.c
index d47b1919e..8012f96b7 100644
--- a/ccache.c
+++ b/ccache.c
@@ -239,6 +239,10 @@ struct pending_tmp_file {
 /* Temporary files to remove at program exit. */
 static struct pending_tmp_file *pending_tmp_files = NULL;
 
+/* PID of currently executing compiler that we have started, if any. 0 means no
+ * ongoing compilation. */
+static pid_t compiler_pid = 0;
+
 /*
  * This is a string that identifies the current "version" of the hash sum
  * computed by ccache. If, for any reason, we want to force the hash sum to be
@@ -339,8 +343,13 @@ clean_up_pending_tmp_files(void)
 static void
 signal_handler(int signo)
 {
+	int status;
 	(void)signo;
 	clean_up_pending_tmp_files();
+	if (compiler_pid != 0) {
+		/* Wait for compiler subprocess to exit before we snuff it. */
+		waitpid(compiler_pid, &status, 0);
+	}
 	_exit(1);
 }
 
@@ -877,7 +886,7 @@ to_cache(struct args *args)
 	}
 
 	cc_log("Running real compiler");
-	status = execute(args->argv, tmp_stdout_fd, tmp_stderr_fd);
+	status = execute(args->argv, tmp_stdout_fd, tmp_stderr_fd, &compiler_pid);
 	args_pop(args, 3);
 
 	if (x_stat(tmp_stdout, &st) != 0) {
@@ -1140,7 +1149,7 @@ get_object_name_from_cpp(struct args *args, struct mdfour *hash)
 		args_add(args, "-E");
 		args_add(args, input_file);
 		cc_log("Running preprocessor");
-		status = execute(args->argv, path_stdout_fd, path_stderr_fd);
+		status = execute(args->argv, path_stdout_fd, path_stderr_fd, &compiler_pid);
 		args_pop(args, 2);
 	}
 
diff --git a/ccache.h b/ccache.h
index 819b7a437..d3ecf6c0c 100644
--- a/ccache.h
+++ b/ccache.h
@@ -213,7 +213,7 @@ void wipe_all(struct conf *conf);
 /* ------------------------------------------------------------------------- */
 /* execute.c */
 
-int execute(char **argv, int fd_out, int fd_err);
+int execute(char **argv, int fd_out, int fd_err, pid_t *pid);
 char *find_executable(const char *name, const char *exclude_name);
 void print_command(FILE *fp, char **argv);
 
diff --git a/execute.c b/execute.c
index f48e67cea..109d60e09 100644
--- a/execute.c
+++ b/execute.c
@@ -223,18 +223,17 @@ win32execute(char *path, char **argv, int doreturn,
 /* Execute a compiler backend, capturing all output to the given paths the full
  * path to the compiler to run is in argv[0]. */
 int
-execute(char **argv, int fd_out, int fd_err)
+execute(char **argv, int fd_out, int fd_err, pid_t *pid)
 {
-	pid_t pid;
 	int status;
 
 	cc_log_argv("Executing ", argv);
-	pid = fork();
-	if (pid == -1) {
+	*pid = fork();
+	if (*pid == -1) {
 		fatal("Failed to fork: %s", strerror(errno));
 	}
 
-	if (pid == 0) {
+	if (*pid == 0) {
 		/* Child. */
 		dup2(fd_out, 1);
 		close(fd_out);
@@ -246,9 +245,10 @@ execute(char **argv, int fd_out, int fd_err)
 	close(fd_out);
 	close(fd_err);
 
-	if (waitpid(pid, &status, 0) != pid) {
+	if (waitpid(*pid, &status, 0) != *pid) {
 		fatal("waitpid failed: %s", strerror(errno));
 	}
+	*pid = 0;
 
 	if (WEXITSTATUS(status) == 0 && WIFSIGNALED(status)) {
 		return -1;
-- 
2.47.2