diff -urN ccache-3.2.1.orig/ccache.c ccache-3.2.1.skip/ccache.c
--- ccache-3.2.1.orig/ccache.c	2014-12-10 22:40:54.000000000 +0300
+++ ccache-3.2.1.skip/ccache.c	2015-03-20 15:39:13.473971831 +0300
@@ -1210,7 +1210,7 @@
  * otherwise NULL. Caller frees.
  */
 static struct file_hash *
-calculate_object_hash(struct args *args, struct mdfour *hash, int direct_mode)
+calculate_object_hash(struct args *args, struct args *preprocessor_args, struct mdfour *hash, int direct_mode)
 {
 	int i;
 	char *manifest_name;
@@ -1422,7 +1422,7 @@
 			cc_log("Did not find object file hash in manifest");
 		}
 	} else {
-		object_hash = get_object_name_from_cpp(args, hash);
+		object_hash = get_object_name_from_cpp(preprocessor_args, hash);
 		cc_log("Got object file hash from preprocessor");
 		if (generating_dependencies) {
 			cc_log("Preprocessor created %s", output_dep);
@@ -1618,7 +1618,7 @@
  */
 bool
 cc_process_args(struct args *args, struct args **preprocessor_args,
-                struct args **compiler_args)
+                struct args **compiler_args, struct args **hashable_args)
 {
 	int i;
 	bool found_c_opt = false;
@@ -1635,7 +1635,7 @@
 	bool dependency_filename_specified = false;
 	/* is the dependency makefile target name specified with -MT or -MQ? */
 	bool dependency_target_specified = false;
-	struct args *expanded_args, *stripped_args, *dep_args, *cpp_args;
+	struct args *expanded_args, *stripped_args, *dep_args, *cpp_args, *nonhash_args;
 	int argc;
 	char **argv;
 	bool result = true;
@@ -1645,6 +1645,7 @@
 	stripped_args = args_init(0, NULL);
 	dep_args = args_init(0, NULL);
 	cpp_args = args_init(0, NULL);
+	nonhash_args = args_init(0, NULL);
 
 	argc = expanded_args->argc;
 	argv = expanded_args->argv;
@@ -1660,7 +1661,7 @@
 				result = false;
 				goto out;
 			}
-			args_add(stripped_args, argv[i]);
+			args_add(nonhash_args, argv[i]);
 			continue;
 		}
 
@@ -2388,11 +2389,18 @@
 	*preprocessor_args = args_copy(stripped_args);
 	args_extend(*preprocessor_args, cpp_args);
 
+	*hashable_args = args_copy(*preprocessor_args);
+
+	/* Append args which we don't want to be hashed */
+	args_extend(*compiler_args, nonhash_args);
+	args_extend(*preprocessor_args, nonhash_args);
+
 out:
 	args_free(expanded_args);
 	args_free(stripped_args);
 	args_free(dep_args);
 	args_free(cpp_args);
+	args_free(nonhash_args);
 	return result;
 }
 
@@ -2587,6 +2595,9 @@
 	struct mdfour direct_hash;
 	struct mdfour cpp_hash;
 
+	/* Arguments (except marked with --ccache-skip) to add to hash */
+	struct args *hash_args;
+
 	/* Arguments (except -E) to send to the preprocessor. */
 	struct args *preprocessor_args;
 
@@ -2628,7 +2639,7 @@
 		conf->direct_mode = false;
 	}
 
-	if (!cc_process_args(orig_args, &preprocessor_args, &compiler_args)) {
+	if (!cc_process_args(orig_args, &preprocessor_args, &compiler_args, &hash_args)) {
 		failed();
 	}
 
@@ -2642,13 +2653,13 @@
 	cc_log("Object file: %s", output_obj);
 
 	hash_start(&common_hash);
-	calculate_common_hash(preprocessor_args, &common_hash);
+	calculate_common_hash(hash_args, &common_hash);
 
 	/* try to find the hash using the manifest */
 	direct_hash = common_hash;
 	if (conf->direct_mode) {
 		cc_log("Trying direct lookup");
-		object_hash = calculate_object_hash(preprocessor_args, &direct_hash, 1);
+		object_hash = calculate_object_hash(hash_args, preprocessor_args, &direct_hash, 1);
 		if (object_hash) {
 			update_cached_result_globals(object_hash);
 
@@ -2682,7 +2693,7 @@
 	 * included_files.
 	 */
 	cpp_hash = common_hash;
-	object_hash = calculate_object_hash(preprocessor_args, &cpp_hash, 0);
+	object_hash = calculate_object_hash(hash_args, preprocessor_args, &cpp_hash, 0);
 	if (!object_hash) {
 		fatal("internal error: object hash from cpp returned NULL");
 	}
diff -urN ccache-3.2.1.orig/ccache.h ccache-3.2.1.skip/ccache.h
--- ccache-3.2.1.orig/ccache.h	2014-12-10 22:40:54.000000000 +0300
+++ ccache-3.2.1.skip/ccache.h	2015-03-18 15:40:12.000000000 +0300
@@ -224,7 +224,7 @@
 
 extern time_t time_of_compilation;
 bool cc_process_args(struct args *args, struct args **preprocessor_args,
-                    struct args **compiler_args);
+                    struct args **compiler_args, struct args **hashable_args);
 void cc_reset(void);
 bool is_precompiled_header(const char *path);
 
diff -urN ccache-3.2.1.orig/test/test_argument_processing.c ccache-3.2.1.skip/test/test_argument_processing.c
--- ccache-3.2.1.orig/test/test_argument_processing.c	2014-12-10 22:40:54.000000000 +0300
+++ ccache-3.2.1.skip/test/test_argument_processing.c	2015-03-20 15:34:23.000000000 +0300
@@ -32,10 +32,10 @@
 TEST(dash_E_should_result_in_called_for_preprocessing)
 {
 	struct args *orig = args_init_from_string("cc -c foo.c -E");
-	struct args *preprocessed, *compiler;
+	struct args *preprocessed, *compiler, *hashable;
 
 	create_file("foo.c", "");
-	CHECK(!cc_process_args(orig, &preprocessed, &compiler));
+	CHECK(!cc_process_args(orig, &preprocessed, &compiler, &hashable));
 	CHECK_INT_EQ(1, stats_get_pending(STATS_PREPROCESSING));
 
 	args_free(orig);
@@ -44,10 +44,10 @@
 TEST(dash_M_should_be_unsupported)
 {
 	struct args *orig = args_init_from_string("cc -c foo.c -M");
-	struct args *preprocessed, *compiler;
+	struct args *preprocessed, *compiler, *hashable;
 
 	create_file("foo.c", "");
-	CHECK(!cc_process_args(orig, &preprocessed, &compiler));
+	CHECK(!cc_process_args(orig, &preprocessed, &compiler, &hashable));
 	CHECK_INT_EQ(1, stats_get_pending(STATS_UNSUPPORTED));
 
 	args_free(orig);
@@ -62,12 +62,15 @@
 	struct args *exp_cpp = args_init_from_string(CMD);
 #undef CMD
 	struct args *exp_cc = args_init_from_string("cc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -85,12 +88,15 @@
 	struct args *exp_cpp = args_init_from_string(CMD);
 #undef CMD
 	struct args *exp_cc = args_init_from_string("cc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -102,12 +108,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"cc -MMD -MFfoo.d -MT mt -MTmt -MQmq");
 	struct args *exp_cc = args_init_from_string("cc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -117,7 +126,7 @@
 	extern char *current_working_dir;
 	char *arg_string;
 	struct args *orig;
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 
 	create_file("foo.c", "");
 	free(conf->base_dir);
@@ -126,12 +135,13 @@
 	arg_string = format("cc --sysroot=%s/foo -c foo.c", current_working_dir);
 	orig = args_init_from_string(arg_string);
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK(str_startswith(act_cpp->argv[1], "--sysroot=./foo"));
 
 	args_free(orig);
 	args_free(act_cpp);
 	args_free(act_cc);
+	args_free(act_hash);
 }
 
 TEST(MF_flag_with_immediate_argument_should_work_as_last_argument)
@@ -141,12 +151,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"cc -MMD -MT bar -MFfoo.d");
 	struct args *exp_cc = args_init_from_string("cc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -158,12 +171,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"cc -MMD -MFfoo.d -MT foo -MTbar");
 	struct args *exp_cc = args_init_from_string("cc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -175,12 +191,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"cc -MMD -MFfoo.d -MQ foo -MQbar");
 	struct args *exp_cc = args_init_from_string("cc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -192,12 +211,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"gcc -MD -MP -MFfoo.d -MQ foo.d");
 	struct args *exp_cc = args_init_from_string("gcc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -209,12 +231,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"gcc -MD -MP -MFfoo.d -MT foo.d");
 	struct args *exp_cc = args_init_from_string("gcc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -226,12 +251,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"gcc -MD -MP -MFfoo.d -MQfoo.d");
 	struct args *exp_cc = args_init_from_string("gcc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -243,12 +271,15 @@
 	struct args *exp_cpp = args_init_from_string(
 		"gcc -MD -MP -MFfoo.d -MTfoo.d");
 	struct args *exp_cc = args_init_from_string("gcc -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -259,7 +290,9 @@
 		"gcc -c -fprofile-generate=some/dir foo.c");
 	struct args *exp_cpp = args_init_from_string("gcc");
 	struct args *exp_cc = args_init_from_string("gcc");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 	char *s;
 
 	create_file("foo.c", "");
@@ -267,13 +300,15 @@
 	mkdir("some/dir", 0777);
 	s = format("-fprofile-generate=%s", x_realpath("some/dir"));
 	args_add(exp_cpp, s);
+	args_add(exp_hash, s);
 	args_add(exp_cc, s);
 	args_add(exp_cc, "-c");
 	free(s);
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }
@@ -286,13 +321,34 @@
 		"gcc -fprofile-generate=some/dir");
 	struct args *exp_cc = args_init_from_string(
 		"gcc -fprofile-generate=some/dir -c");
-	struct args *act_cpp = NULL, *act_cc = NULL;
+	/* hashable args are the same as preprocessor, unless there's --ccache-skip */
+	struct args *exp_hash = args_copy(exp_cpp);
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
 
 	create_file("foo.c", "");
 
-	CHECK(cc_process_args(orig, &act_cpp, &act_cc));
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
 	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
 	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
+
+	args_free(orig);
+}
+
+TEST(ccache_skip_flag_should_affect_hashing)
+{
+	struct args *orig = args_init_from_string("cc -c foo.c --ccache-skip -DSOME");
+	struct args *exp_cpp = args_init_from_string("cc -DSOME");
+	struct args *exp_cc = args_init_from_string("cc -c -DSOME");
+	struct args *exp_hash = args_init_from_string("cc");
+	struct args *act_cpp = NULL, *act_cc = NULL, *act_hash = NULL;
+
+	create_file("foo.c", "");
+
+	CHECK(cc_process_args(orig, &act_cpp, &act_cc, &act_hash));
+	CHECK_ARGS_EQ_FREE12(exp_cpp, act_cpp);
+	CHECK_ARGS_EQ_FREE12(exp_cc, act_cc);
+	CHECK_ARGS_EQ_FREE12(exp_hash, act_hash);
 
 	args_free(orig);
 }