Improve fix in #400 to handle more cases

The dependency file name can come from e.g. DEPENDENCIES_OUTPUT as well,
so hash information about a /dev/null .d file after the argument
processing loop instead.

2 files changed, 19 insertions, 3 deletions

diff --git a/src/ccache.c b/src/ccache.c
index 2d2a96eb..251783ac 100644
--- a/src/ccache.c
+++ b/src/ccache.c
@@ -2049,9 +2049,6 @@ calculate_object_hash(struct args *args, struct hash *hash, int direct_mode)
 						// Next argument is dependency name, so skip it.
 						i++;
 					}
-				} else {
-					// Hash that we don't have a .d file.
-					hash_string(hash, output_dep);
 				}
 				continue;
 			}
@@ -2112,6 +2109,12 @@ calculate_object_hash(struct args *args, struct hash *hash, int direct_mode)
 		}
 	}
 
+	// Make results with dependency file /dev/null different from those without
+	// it.
+	if (generating_dependencies && str_eq(output_dep, "/dev/null")) {
+		hash_delimiter(hash, "/dev/null dependency file");
+	}
+
 	if (!found_ccbin && str_eq(actual_language, "cuda")) {
 		hash_nvcc_host_compiler(hash, NULL, NULL);
 	}
diff --git a/test/suites/direct_gcc.bash b/test/suites/direct_gcc.bash
index 4eb9bf6b..ad5b490d 100644
--- a/test/suites/direct_gcc.bash
+++ b/test/suites/direct_gcc.bash
@@ -139,4 +139,17 @@ SUITE_direct_gcc() {
     expect_stat 'cache miss' 1
     expect_equal_files different_name.d expected_sunpro_dependencies_target.d
     expect_equal_object_files reference_test.o test.o
+
+    # -------------------------------------------------------------------------
+    TEST "DEPENDENCIES_OUTPUT environment variable set to /dev/null"
+
+    DEPENDENCIES_OUTPUT="/dev/null" $CCACHE_COMPILE -c test.c
+    expect_stat 'cache hit (direct)' 0
+    expect_stat 'cache hit (preprocessed)' 0
+    expect_stat 'cache miss' 1
+
+    DEPENDENCIES_OUTPUT="other.d" $CCACHE_COMPILE -c test.c
+    expect_stat 'cache hit (direct)' 0
+    expect_stat 'cache hit (preprocessed)' 0
+    expect_stat 'cache miss' 2
 }