patches/ccache-2.4-dependency-output.patch

diff -urbN ccache-2.4-org/ccache.c ccache-2.4/ccache.c
--- ccache-2.4-org/ccache.c	2006-12-05 10:46:11.000000000 +0100
+++ ccache-2.4/ccache.c	2006-12-14 00:50:00.000000000 +0100
@@ -65,6 +65,9 @@
 /* can we safely use the unification hashing backend? */
 static int enable_unify;
 
+/* the name of the dependency file to output when -MD is used */
+static char  *dependency_file;
+
 /* a list of supported file extensions, and the equivalent
    extension for code that has been through the pre-processor
 */
@@ -364,10 +367,17 @@
 
 	if (!direct_i_file) {
 		/* run cpp on the input file to obtain the .i */
+		if (dependency_file) {
+			args_add(args, "-MD" );
+			args_add(args, "-MF" );
+			args_add(args, dependency_file);
+			args_add(args, "-MQ" );
+			args_add(args, output_file);
+		}
 		args_add(args, "-E");
 		args_add(args, input_file);
 		status = execute(args->argv, path_stdout, path_stderr);
-		args_pop(args, 2);
+		args_pop(args, dependency_file ? 7 : 2);
 	} else {
 		/* we are compiling a .i or .ii file - that means we
 		   can skip the cpp stage and directly form the
@@ -625,10 +635,12 @@
 	int i;
 	int found_c_opt = 0;
 	int found_S_opt = 0;
+	int found_MD_opt = 0;
 	struct stat st;
 	char *e;
 
 	stripped_args = args_init(0, NULL);
+	dependency_file = NULL;
 
 	args_add(stripped_args, argv[0]);
 
@@ -663,6 +675,11 @@
 			continue;
 		}
 		
+		if (strcmp(argv[i], "-MD") == 0) {
+			found_MD_opt = 1;
+			continue;
+		}
+
 		/* we need to work out where the output was meant to go */
 		if (strcmp(argv[i], "-o") == 0) {
 			if (i == argc-1) {
@@ -814,6 +831,21 @@
 		p[2] = 0;
 	}
 
+	/* the -MD option is used to generate dependency output alongside the compilation */
+	if (found_MD_opt) {
+		char *p;
+
+		dependency_file = x_strdup(output_file);
+		p = strrchr( dependency_file, '.' );
+		if (!p || !p[1]) {
+			cc_log("badly formed dependency_file %s\n", dependency_file);
+			stats_update(STATS_ARGS);
+			failed();
+		}
+		p[1] = 'd';
+		p[2] = 0;
+	}
+
 	/* cope with -o /dev/null */
 	if (strcmp(output_file,"/dev/null") != 0 && stat(output_file, &st) == 0 && !S_ISREG(st.st_mode)) {
 		cc_log("Not a regular file %s\n", output_file);