diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/ccache.c ccache-gsplit-dwarf-support/ccache.c
--- ccache/ccache.c	2015-03-04 23:01:48.149927458 +0900
+++ ccache-gsplit-dwarf-support/ccache.c	2015-03-06 01:36:08.254903827 +0900
@@ -1,3 +1,4 @@
+/*   -*- mode: C; fill-column:78  -*- */
 /*
  * ccache -- a fast C/C++ compiler cache
  *
@@ -39,7 +40,7 @@ static const char VERSION_TEXT[] =
 MYNAME " version %s\n"
 "\n"
 "Copyright (C) 2002-2007 Andrew Tridgell\n"
-"Copyright (C) 2009-2011 Joel Rosdahl\n"
+"Copyright (C) 2009-2015 Joel Rosdahl\n"
 "\n"
 "This program is free software; you can redistribute it and/or modify it under\n"
 "the terms of the GNU General Public License as published by the Free Software\n"
@@ -95,9 +96,12 @@ static char *output_obj;
 /* The path to the dependency file (implicit or specified with -MF). */
 static char *output_dep;
 
-/* Diagnostic generation information (clang). */
+/* Diagnostic generation information (clang). Contains pathname if not NULL. */
 static char *output_dia = NULL;
 
+/* -gsplit-dwarf support: Split dwarf information (GCC 4.8 and up). Contains pathname if not NULL. */
+static char *output_dwo = NULL;
+
 /*
  * Name (represented as a struct file_hash) of the file containing the cached
  * object code.
@@ -129,6 +133,21 @@ static char *cached_dep;
 static char *cached_dia;
 
 /*
+ * -gsplit-dwarf support:
+ * Full path to the file containing the split dwarf (for GCC 4.8 and above)
+ * (cachedir/a/b/cdef[...]-size.dwo).
+ *
+ * contains NULL if -gsplit-dwarf is not given.
+ */
+static char *cached_dwo;
+
+/*
+ * -gsplit-dwarf support:
+ * split_dwarf_p is true  if "-gsplit-dwarf" is given to the compiler (GCC 4.8 and up).
+ */
+bool split_dwarf_p = false;
+
+/*
  * Full path to the file containing the manifest
  * (cachedir/a/b/cdef[...]-size.manifest).
  */
@@ -261,6 +280,7 @@ failed(void)
 	fatal("execv of %s failed: %s", orig_args->argv[0], strerror(errno));
 }
 
+
 static const char *
 temp_dir()
 {
@@ -735,18 +755,66 @@ static void
 to_cache(struct args *args)
 {
 	char *tmp_stdout, *tmp_stderr;
+	char *tmp_dwo;	/* for supporting -gsplit-dwarf */
+	char *cp;	/* for supporting -gsplit-dwarf */
 	struct stat st;
 	int status, tmp_stdout_fd, tmp_stderr_fd;
 
+	/* Here cached_obj contains a file name for object */
+
 	tmp_stdout = format("%s.tmp.stdout", cached_obj);
 	tmp_stdout_fd = create_tmp_fd(&tmp_stdout);
 	tmp_stderr = format("%s.tmp.stderr", cached_obj);
 	tmp_stderr_fd = create_tmp_fd(&tmp_stderr);
 
+	/* -gsplit-dwarf support: creating .dwo file name
+	 *
+	 * What is the reliable way of creating the .dwo file name in the case
+	 * of using |-o output_obj| to the compiler ?
+	 * Heuristics based on one run of GCC 4.8 is placed below, and it
+	 * works with gcc 4.9 as well.
+	 *
+	 * No matter whether -gsplit-warning is placed on the command line, or
+	 * if so, whether it has been seen or not, we need to set tmp_dwo in
+	 * this part of the code to reflect the value of the current output_obj
+	 * to tmp_dwo.
+	 * If -gsplit-dwarf is specified on the command line, this tmp_dwo
+	 * will be used.
+	 */
+
+	// In the extreme simple case,
+	// Try replacing .o with .dwo.
+	//
+	// Fact: gcc-4.8 produced the following .dwo file for the command
+	// below:
+	// t-test.o.tmp.dwo
+	//
+	//  /usr/bin/gcc-4.8 -gsplit-dwarf -c t-test.c -o t-test.o.tmp.gazonk
+	//
+	// So here is the huristics (works with gcc 4.9 also).
+	// Strip anything after the final '.' and add "dwo" instead.
+
+	// TODO/FIXME: CHANGED. No more output_to_real_object_first
+	cp =  strrchr(output_obj, '.');
+	assert(cp);
+	{
+		/*
+		 * String is modified in place. Since we already created the
+		 * string by x_strdup, and format, we should be relatively
+		 * safe and not cause unintended change even if ccache becomes
+		 * multi-threaded.
+		 */
+		*cp = '\0';
+		tmp_dwo = format("%s.dwo", output_obj);
+		*cp = '.';
+	}
+	cc_log("Setting tmp_dwo to %s", tmp_dwo);
+
 	args_add(args, "-o");
 	args_add(args, output_obj);
 
 	if (output_dia) {
+		cc_log("(output_dia) Outputting to final destination: %s", output_dia);
 		args_add(args, "--serialize-diagnostics");
 		args_add(args, output_dia);
 	}
@@ -774,6 +842,9 @@ to_cache(struct args *args)
 		stats_update(STATS_MISSING);
 		tmp_unlink(tmp_stdout);
 		tmp_unlink(tmp_stderr);
+		/* -gsplit-dwarf support requires the removal of a few more files.*/
+		if (tmp_dwo)
+			tmp_unlink(tmp_dwo);
 		failed();
 	}
 	if (st.st_size != 0) {
@@ -781,11 +852,20 @@ to_cache(struct args *args)
 		stats_update(STATS_STDOUT);
 		tmp_unlink(tmp_stdout);
 		tmp_unlink(tmp_stderr);
+		/* -gsplit-dwarf support requires the removal of a few more files. */
+		if (tmp_dwo) {
+			tmp_unlink(tmp_dwo);
+		}
 		failed();
 	}
 	tmp_unlink(tmp_stdout);
 
 	/*
+	 *  OBSERVATION: processing stderr does not have to be changed in the
+	 *  presence of "-gsplit-dwarf".
+	 */
+
+	/*
 	 * Merge stderr from the preprocessor (if any) and stderr from the real
 	 * compiler into tmp_stderr.
 	 */
@@ -838,26 +918,87 @@ to_cache(struct args *args)
 			close(fd);
 			tmp_unlink(tmp_stderr);
 
+			/* Copying of _dia file should be done here since when
+			 * an error occurs, we may want to know the
+			 * diagnostics, don't we?
+			 * As it turns out since we now generate always first in the final destination
+			 * the following code is not necessary (?).
+			 * I comment it out using #if 0/#endif for now.
+			 */
+#if 0 
+			if (output_dia) {
+				int ret;
+				x_unlink(output_dia);
+				/* only make a hardlink if the cache file is uncompressed */
+				ret = move_file(tmp_dia, output_dia, 0);
+
+				if (ret == -1) {
+					if (errno == ENOENT) {
+						/* Someone removed the file just before we began copying? */
+						cc_log("Diagnostic file %s just disappeared", output_dia);
+						stats_update(STATS_MISSING);
+					} else {
+						cc_log("Failed to move %s to %s: %s",
+						       tmp_dia, output_dia, strerror(errno));
+						stats_update(STATS_ERROR);
+						failed();
+					}
+					x_unlink(tmp_dia);
+				} else {
+					cc_log("Created %s from %s", output_dia, tmp_dia);
+				}
+			}
+#endif
+
 			exit(status);
 		}
 
+		cc_log("verbose: (tmp_stderr) %s being removed", tmp_stderr);
 		tmp_unlink(tmp_stderr);
+
+		/* gsplit-support modification */
+		if (tmp_dwo) {
+			tmp_unlink(tmp_dwo);
+		}
 		failed();
 	}
 
 	if (stat(output_obj, &st) != 0) {
-		cc_log("Compiler didn't produce an object file");
+		cc_log("(output_obj) Compiler didn't produce an object file");
 		stats_update(STATS_NOOUTPUT);
 		failed();
 	}
 	if (st.st_size == 0) {
-		cc_log("Compiler produced an empty object file");
+		cc_log("(output_obj) Compiler produced an empty object file");
 		stats_update(STATS_EMPTYOUTPUT);
 		failed();
 	}
 
+
+	/* -gsplit-dwarf support:
+	 * We should also repeat the check for .dwo file in addition to
+	 * output_obj when "-gsplit-dwarf is given.
+	 * Because of the way tmp_dwo is produced when command line is
+	 * scanned, we can have non-null tmp_dwo even when split_swarf_p is
+	 * false.  Check only when split_dwarf_p is true.
+	 */
+
+	if (tmp_dwo && split_dwarf_p) {
+		/* cc_log("tmp_dwo = %s", tmp_dwo); */
+		if (stat(tmp_dwo, &st) != 0) {
+			cc_log("(tmp_dwo) Compiler didn't produce a split dwarf file");
+			stats_update(STATS_NOOUTPUT);
+			failed();
+		}
+		if (st.st_size == 0) {
+			cc_log("(tmp_dwo) Compiler produced an empty split dwarf file");
+			stats_update(STATS_EMPTYOUTPUT);
+			failed();
+		}
+	}
+
 	if (stat(tmp_stderr, &st) != 0) {
-		cc_log("Failed to stat %s: %s", tmp_stderr, strerror(errno));
+		cc_log("(tmp_stderr) Failed to stat %s: %s", tmp_stderr, strerror(errno));
 		stats_update(STATS_ERROR);
 		failed();
 	}
@@ -865,16 +1006,30 @@ to_cache(struct args *args)
 		if (move_uncompressed_file(
 			    tmp_stderr, cached_stderr,
 			    conf->compression ? conf->compression_level : 0) != 0) {
-			cc_log("Failed to move %s to %s: %s", tmp_stderr, cached_stderr,
-			       strerror(errno));
+			cc_log("Failed to move %s to %s: %s",
+			       tmp_stderr, cached_stderr, strerror(errno));
 			stats_update(STATS_ERROR);
 			failed();
 		}
-		cc_log("Stored in cache: %s", cached_stderr);
+		cc_log("(cached_stderr) Stored in cache: %s", cached_stderr);
+		/*
+		 * Do not forget to check return value of stat() and act
+		 * accordingly.
+		 */
 		if (conf->compression) {
-			stat(cached_stderr, &st);
+			/*
+			 * The file was compressed, so obtain the compressed
+			 * size again.
+			 */
+			if ( stat(cached_stderr, &st) == 0) {
+				stats_update_size(file_size(&st), 1);
+			} else {
+				cc_log("stat on cached_stderr=%s failed (%s)",
+				       cached_stderr, strerror(errno));
+			}
+		} else {
+			stats_update_size(file_size(&st), 1);
 		}
-		stats_update_size(file_size(&st), 1);
 	} else {
 		tmp_unlink(tmp_stderr);
 		if (conf->recache) {
@@ -885,16 +1040,62 @@ to_cache(struct args *args)
 
 	if (output_dia) {
 		if (stat(output_dia, &st) != 0) {
-			cc_log("Failed to stat %s: %s", output_dia, strerror(errno));
+			cc_log("(output_dia) Failed to stat %s: %s", output_dia, strerror(errno));
 			stats_update(STATS_ERROR);
 			failed();
 		}
 		if (st.st_size > 0) {
 			put_file_in_cache(output_dia, cached_dia);
+			cc_log("(cached_dia) Stored in cache: %s", cached_dia);
 		}
 	}
 
-	put_file_in_cache(output_obj, cached_obj);
+	/* Description of processing below.:
+  	 * Perform the copy of .dwo file if --gsplit-dwarf is used.
+	 */
+
+ 	put_file_in_cache(output_obj, cached_obj);
+
+	cc_log("(cached_obj) Stored in cache: %s", cached_obj);
+
+	/* stats_update(STATS_TOCACHE) is now called AFTER the processing of
+         * .dwo file below.
+	 */
+
+	/*
+	 * Caution: if we output to real object file first, then
+	 * output_obj *IS* the real object, and so we should not remove it!
+	 * And this operation mode *IS* the default!
+	 *
+	 * Also, in this case, we should NOT copy back the cached file to the
+	 * final destination object. This is a waste of time.
+	 *
+	 * Same can be said of .dwo file: real and cached one below.
+	 * Somehow dependency file was not copied this way.
+	 */
+
+	/* -gsplit-dwarf support:
+	 * if -gsplit-dwarf is given on the compiler command line,
+	 * .dwo file ought to be put into cache as well.
+	 */
+	if (split_dwarf_p)
+	{
+		assert(tmp_dwo);
+		assert(cached_dwo);
+		put_file_in_cache(tmp_dwo, cached_dwo);
+		cc_log("(cached_dwo) Stored in cache: %s", cached_dwo);
+
+		/* internal sanity check */
+		if (!generating_dependencies)
+			assert(tmp_dwo && cached_dwo);
+
+		/* Caution: if we output to real object file first, then
+		 * tmp_dwo *IS* the real .dwo file, and so we should not remove it!
+		 * The original code is left as a comment line to stress this point.
+		 */
+		/* tmp_unlink(tmp_dwo); */
+	}
+
 	stats_update(STATS_TOCACHE);
 
 	/* Make sure we have a CACHEDIR.TAG in the cache part of cache_dir. This can
@@ -915,13 +1116,15 @@ to_cache(struct args *args)
 		 * previous ccache versions. */
 		if (getpid() % 1000 == 0) {
 			char *path = format("%s/CACHEDIR.TAG", conf->cache_dir);
-			unlink(path);
+			x_unlink(path);
 			free(path);
 		}
 	}
 
 	free(tmp_stderr);
 	free(tmp_stdout);
+	if (tmp_dwo)
+		free(tmp_dwo);
 }
 
 /*
@@ -1045,6 +1248,29 @@ update_cached_result_globals(struct file
 	cached_stderr = get_path_in_cache(object_name, ".stderr");
 	cached_dep = get_path_in_cache(object_name, ".d");
 	cached_dia = get_path_in_cache(object_name, ".dia");
+
+	/*
+	 * --gsplit-dwarf support.
+	 * We set cached_dwo to NULL to signify --gsplit-dwarf is not used.
+	 */
+	if (split_dwarf_p)
+		cached_dwo    = get_path_in_cache(object_name, ".dwo");
+	else
+		cached_dwo    = NULL;
+
+	/* TODO/NOTE: if split_dwarf_p is not true and we get non-null
+	 * get_path_in_cache(object_name, ".dwo"), we probably should purge
+	 * that file! But this is not so critical. We will purge the file eventually
+	 * by LRU algorithm.
+	 */
+	if (!split_dwarf_p) {
+		char *cp;
+		cp =  get_path_in_cache(object_name, ".dwo");
+		if (!cp) {
+			cc_log("We are not using split dwarf but, we have .dwo. Maybe we should purge it.:%s", cp);
+		}
+	}
+
 	stats_file = format("%s/%c/stats", conf->cache_dir, object_name[0]);
 	free(object_name);
 }
@@ -1335,6 +1561,12 @@ calculate_object_hash(struct args *args,
 		hash_delimiter(hash, "-fprofile-dir");
 		hash_string(hash, profile_dir);
 	}
+	/* OBSERVATION: processing for profile_use is a good example
+	 * which we can mimic to implement the support for
+	 * --gsplit-dwarf.
+	 * So the support for -gsplit-dwarf was modeled after the
+	 * processing to support profile.
+	 */
 	if (profile_use) {
 		/* Calculate gcda name */
 		char *gcda_name;
@@ -1420,6 +1652,7 @@ static void
 from_cache(enum fromcache_call_mode mode, bool put_object_in_manifest)
 {
 	int fd_stderr;
+	int ret;		/* to keep track of error value. */
 	struct stat st;
 	bool produce_dep_file;
 
@@ -1428,28 +1661,59 @@ from_cache(enum fromcache_call_mode mode
 		return;
 	}
 
-	/* Check if the object file is there. */
+	/*
+	 * Check if the object file is there.
+	 * For -gsplit-dwarf support, check for .dwo as well. See below.
+	 * cached_obj contains the path for cached object file.
+	 */
+
 	if (stat(cached_obj, &st) != 0) {
-		cc_log("Object file %s not in cache", cached_obj);
+		cc_log("(cached_obj) Object file %s not in cache", cached_obj);
 		return;
 	}
 
-	/* Check if the diagnostic file is there. */
+	/* Check if the diagnostic file is there.
+	 * Notice the logic. We only check when output_dia is not NULL.
+	 */
 	if (output_dia && stat(cached_dia, &st) != 0) {
-		cc_log("Diagnostic file %s not in cache", cached_dia);
+		cc_log("(cached_dia) Diagnostic file %s not in cache", cached_dia);
 		return;
 	}
 
 	/*
 	 * Occasionally, e.g. on hard reset, our cache ends up as just filesystem
-	 * meta-data with no content catch an easy case of this.
+	 * meta-data with no content. Catch an easy case of this.
 	 */
 	if (st.st_size == 0) {
-		cc_log("Invalid (empty) object file %s in cache", cached_obj);
+		cc_log(" (cached_obj) Invalid (empty) object file %s in cache", cached_obj);
 		x_unlink(cached_obj);
 		return;
 	}
 
+	/* -gsplit-dwarf support
+	 * We should repeat the above check for cached_dwo
+	 */
+	if (split_dwarf_p && !generating_dependencies)
+		assert(output_dwo);
+
+	if (output_dwo)
+		assert(cached_dwo);
+
+	if (output_dwo) {
+
+		if (stat(cached_dwo, &st) != 0) {
+			cc_log("(cached_dwo) Split dwarf file %s not in cache", cached_dwo);
+			return;
+		}
+
+		if (st.st_size == 0) {
+			cc_log(" (cached_dwo) Invalid (empty) dwo file %s in cache", cached_dwo);
+			x_unlink(cached_dwo);
+			x_unlink(cached_obj); /* to really invalidate */
+			return;
+		}
+	}
+
 	/*
 	 * (If mode != FROMCACHE_DIRECT_MODE, the dependency file is created by
 	 * gcc.)
@@ -1462,16 +1726,117 @@ from_cache(enum fromcache_call_mode mode
 		return;
 	}
 
-	if (!str_eq(output_obj, "/dev/null")) {
-		get_file_from_cache(cached_obj, output_obj);
+	/*
+	 * Note: The if-expr is reverted. In the else clause, do a similar
+	 * processing for FissionDwarf file, cached_dwo in case -gsplit-dwarf
+	 * is specified.
+	 */
+
+	if (str_eq(output_obj, "/dev/null")) {
+		ret = 0;
+	} else { /* not /dev/null */
+		/* we get file(s) from cache unless we generate object in direct mode */
+		/* output_to_real_object_first &&  <=== TRUE always now*/
+		if (mode == FROMCACHE_COMPILED_MODE /* called compier */) {
+			/* we don't need to copy from cache since we have
+			   called the compiler and left the object in the
+			   final destination.*/
+			cc_log("[direct object generation]: skipped copy: (output_obj) %s from (cached_obj) %s",
+			       output_obj, cached_obj);
+
+		} else {
+			/* internal sanity check */
+			assert( /* output_to_real_object_first : TRUE always now.*/
+				(mode == FROMCACHE_CPP_MODE
+				 || mode == FROMCACHE_DIRECT_MODE)
+				/* || (!output_to_real_object_first) FALSE always now.*/
+				);
+			get_file_from_cache(cached_obj, output_obj);
+			cc_log("Created (output_obj) %s from (cached_obj) %s",
+			       output_obj, cached_obj);
+		}
+
+		/*
+		 * if something failed internal to get_file_from_cache we may
+		 * want to remove some files: the following x_unlink calls
+		 * were in the original code circa 2014 summer.
+		 *
+		 * Similar comments are repeated in code below.
+		 *
+		 * Does failed(), which is called when error exit is taken,
+		 * handle this now?  If so, this comment is superflous.
+		 *
+		 * if (output_dwo) x_unlink(output_dwo);
+		 * if (cached_dwo) x_unlink(cached_dwo);
+		 * x_unlink(output_obj);
+		 * x_unlink(cached_stderr);
+		 * x_unlink(cached_obj);
+		 * x_unlink(cached_dep);
+		 *x_unlink(cached_dia);
+		 */
+		ret = 0;
 	}
+
+	assert(ret == 0);
+	if (split_dwarf_p) {
+		assert(output_dwo);
+		/* assert(output_to_real_object_first); implicitly true now. */
+		/*
+		 * we don't need to get file from cache when we called tge
+		 * compiler in this run of ccache since the output_dwo would
+		 * have been created by the compiler.
+		 */
+		if (mode == FROMCACHE_CPP_MODE || mode == FROMCACHE_DIRECT_MODE ) {
+			/* did not call compiler */
+			get_file_from_cache(cached_dwo, output_dwo);
+			/*
+			 * Note: if something failed internal to get_file_from_cache
+			 * we may want to remove a flurry of files.
+			 * There were calls to x_unlinks in the original code circa 2014 summer.
+			 */
+		} else {
+			/* sanity check */
+			assert(mode == FROMCACHE_COMPILED_MODE);
+			cc_log("[direct object generation]: skipped the copy from cached_dwo=%s  to output_dwo=%s",
+			       cached_dwo, output_dwo);
+		}
+	}
+
+	/* NOTE: The error processing above assumed we only do a copy/hardlink
+	 * for cached_obj.  We may need to repeat the copy and error
+	 * processing for cached_dwo in a similar manner instead of doing the
+	 * copy/link only.
+	 *
+	 * But do note that the unlinking of related files
+	 * MUST BE REPEATED in the both cases of the failures of copy/link
+	 * of  cached_obj -> output_obj
+	 * and cached_dwo -> output_dwo if (split_dwarf_p).
+         */
+
 	if (produce_dep_file) {
 		get_file_from_cache(cached_dep, output_dep);
+		cc_log("Created (output_dep) %s from (cached_dep) %s", output_dep, cached_dep);
+		/*
+		 * Note: if something failed internal to get_file_from_cache
+		 * we may want to remove a flurry of files.
+		 * There were calls to x_unlinks in the original code circa 2014 summer.
+		 */
 	}
 	if (output_dia) {
 		get_file_from_cache(cached_dia, output_dia);
+		cc_log("Created (output_dia) %s from (cached_dia) %s", output_dia, cached_dia);
+
+		/*
+		 * Note: if something failed internal to get_file_from_cache
+		 * we may want to remove a flurry of files.
+		 * There were calls to x_unlinks in the original code circa 2014 summer.
+		 */
 	}
 
+	/* OBSERVATION: The above seems to be the best place where we
+	 * can copy object file and dwo file safely.
+	 */
+
 	/* Update modification timestamps to save files from LRU cleanup.
 	   Also gives files a sensible mtime when hard-linking. */
 	update_mtime(cached_obj);
@@ -1487,13 +1852,20 @@ from_cache(enum fromcache_call_mode mode
 		put_file_in_cache(output_dep, cached_dep);
 	}
 
+	/*  -gsplit-dwarf support */
+	if (cached_dwo)
+		update_mtime(cached_dwo);
+
 	/* Send the stderr, if any. */
 	fd_stderr = open(cached_stderr, O_RDONLY | O_BINARY);
 	if (fd_stderr != -1) {
+		cc_log("Using stderr cache (cached_stderr): %s\n", cached_stderr);
 		copy_fd(fd_stderr, 2);
 		close(fd_stderr);
 	}
 
+	/* Note: we do not need to put .dwo file in MANIFEST file. */
+
 	/* Create or update the manifest file. */
 	if (conf->direct_mode
 	    && put_object_in_manifest
@@ -1508,8 +1880,16 @@ from_cache(enum fromcache_call_mode mode
 		if (manifest_put(manifest_path, cached_obj_hash, included_files)) {
 			cc_log("Added object file hash to %s", manifest_path);
 			update_mtime(manifest_path);
-			stat(manifest_path, &st);
-			stats_update_size(file_size(&st) - old_size, old_size == 0 ? 1 : 0);
+			/*
+			 * Don't forget to check the return value of stat and act accordingly.
+			 */
+			if (stat(manifest_path, &st) == 0) {
+				stats_update_size((file_size(&st) - old_size),
+						  old_size == 0 ? 1 : 0);
+			} else {
+				cc_log("stat on manifest (manifest_path) %s failed (%s), so size statistics is incorrect.",
+				       manifest_path, strerror(errno));
+			}
 		} else {
 			cc_log("Failed to add object file hash to %s", manifest_path);
 		}
@@ -1659,6 +2039,7 @@ cc_process_args(struct args *args, struc
 			if (argpath[-1] == '-') {
 				++argpath;
 			}
+
 			file_args = args_init_from_gcc_atfile(argpath);
 			if (!file_args) {
 				cc_log("Couldn't read arg file %s", argpath);
@@ -1755,6 +2136,12 @@ cc_process_args(struct args *args, struc
 				goto out;
 			}
 			output_obj = make_relative_path(x_strdup(argv[i+1]));
+
+			/* OBSERVATION: We need to create output_dwo if
+			   -gsplit-dwarf is given.  But we should not do here
+			   YET since --gsplit-dwarf may be given later on the
+			   command line !*/
+
 			i++;
 			continue;
 		}
@@ -1765,6 +2152,20 @@ cc_process_args(struct args *args, struc
 			continue;
 		}
 
+		/* -gsplit-dwarf support
+		 * This place is chosen as the place to handle -gsplit-dwarf.
+		 */
+
+		if (str_eq(argv[i], "-gsplit-dwarf")) {
+			cc_log("split_dwarf_p is set to true due to -gsplit-dwarf.");
+			split_dwarf_p = true;
+			// output_to_real_object_first = true;
+			/* we should add this option to the compiler option
+			   when the real compiler is invoked. */
+			args_add(stripped_args, argv[i]);
+			continue;
+		}
+
 		/* debugging is handled specially, so that we know if we
 		   can strip line number info
 		*/
@@ -2154,6 +2555,20 @@ cc_process_args(struct args *args, struc
 
 		/* Rewrite to relative to increase hit rate. */
 		input_file = make_relative_path(x_strdup(argv[i]));
+	} /* for */
+
+	/* found_S_opt needs to be handled with caution with split_dwarf_p */
+
+	if (found_S_opt /* || generating_dependencies*/ ) {
+		/* even if -gsplit-dwarf is given, .dwo file is not generated.
+		 * So split_dwarf_p is set to false.
+		 *
+		 * Note: Just a tidbit. When -S is given on the command line,
+		 * the cached .o file in the cache spool actually has .o
+		 * suffix. Interesting, isn't it?
+		 */
+		split_dwarf_p = false;
+		cc_log("split_dwarf_p is reset to false due to found_S_opt");
 	}
 
 	if (!input_file) {
@@ -2241,6 +2656,15 @@ cc_process_args(struct args *args, struc
 		conf->cpp_extension = x_strdup(extension_for_language(p_language) + 1);
 	}
 
+	/* Question: Is there an angle in which split_dwarf_p processing has
+	 * anything to do with "-" output that is handled specialy below?
+	 *
+	 * For example, what do we want to do with .dwo file (produce it
+	 * somewhere, but what path name to use)?
+	 *
+	 * We may find the answer in the long run.
+	 */
+
 	/* don't try to second guess the compilers heuristics for stdout handling */
 	if (output_obj && str_eq(output_obj, "-")) {
 		stats_update(STATS_OUTSTDOUT);
@@ -2249,6 +2673,53 @@ cc_process_args(struct args *args, struc
 		goto out;
 	}
 
+	/* -gsplit-dwarf support:
+	 * We have probably already seen and check for
+	 * -gsplit-dwarf by the time we reach here. (We did it somewhere above.)
+	 * Here is the chance to create output_dwo based on the value of output_obj.
+	 * The basic outline would be
+	 * output_obj = basename(input_file)
+	 * add ".dwo" to it with minor tweaks to handle special cases.
+	 */
+
+	/*
+	 * Special case 1: What do we do if we need to output .s file
+	 * for output and -gsplit-dwarf is specified?
+	 * What file(s) does GCC 4.8 produce exactly?
+	 * Answer:
+	 * /usr/bin/gcc-4.8 -gsplit-dwarf -c t-test.c -S
+	 * generated
+	 * t-test.s
+	 * that contains assembler directives to generate data (dwarf data).
+	 * This means that if we are only producing assembler source
+	 * we do not need to handle ".dwo" file at all.
+	 *
+	 * /usr/bin/gcc-4.8 -gsplit-dwarf -c t-test.c -S -o t-test.s.gazonk
+	 * produced
+	 * t-test.s.gazonk
+	 *
+	 * DONE:
+	 * The above special cases need to be handled.
+	 * The modification below more or less assumed that .dwo file is produced
+	 * always (together with the paired .o file) unless "-S" is specified.
+	 *
+	 * File-scope global variable |found_S_opt| is set to true
+	 * when "-S" is specified.
+	 *
+	 * /usr/bin/gcc-4.8 -gsplit-dwarf -c t-test.s
+	 * produced
+	 * t-test.o
+	 * t-test.o.dwo.
+	 *
+	 * So let us disable split_dwarf_p to false if
+	 * found_S_opt is true.
+	 * This is done at the end of a loop in argument processing.
+	 */
+
+	/*
+	 * We always use |output_obj| even in the case of "-gsplit-dwarf"
+	 * in the code below.
+	 */
 	if (!output_obj) {
 		if (output_is_precompiled_header) {
 			output_obj = format("%s.gch", input_file);
@@ -2267,6 +2738,31 @@ cc_process_args(struct args *args, struc
 		}
 	}
 
+	/* -gsplit-dwarf support: create output_dwo */
+	if (split_dwarf_p && !found_S_opt) {
+		char *p;
+		p = strrchr(output_obj, '.');
+		if (!p || !p[1]) {
+			cc_log("Badly formed object filename");
+			stats_update(STATS_ARGS);
+			result = false;
+			goto out;
+		}
+		*p = '\0';
+		output_dwo = format("%s.dwo", output_obj);
+		*p = '.';
+
+		cc_log("setting output_dwo to %s", output_dwo);
+	}
+
+
+	/* Long-term question: Do we need to cope with strange output_obj file
+	 * name in case split_dwarf_p?
+	 * "-gsplit-dwarf" support may encounter corner cases when strange
+	 * file names are given.
+	 * We may find the answer in the long run.
+	 */
+
 	/* cope with -o /dev/null */
 	if (!str_eq(output_obj,"/dev/null")
 	    && stat(output_obj, &st) == 0
@@ -2317,6 +2813,20 @@ cc_process_args(struct args *args, struc
 		}
 	}
 
+	/* -gsplit-dwarf support: Ordering of dependency generation.
+	 *
+	 * -gsplit-dwarf processing should not affect dependency generation.
+	 *
+	 * Note, given the command line below, dependency file is generated
+	 * first and then ccache.o is generated.
+	 * Observing the ordering and take care of that.
+	 *
+	 * ccache /usr/bin/gcc-4.8 -gsplit-dwarf -DHAVE_CONFIG_H              \
+	 * -DSYSCONFDIR=/usr/local/etc -I. -I.  -MD -MP -MF .deps/ccache.c.d  \
+	 * -g -O2 -Wall -W -Werror -c -o ccache.o ccache.c
+	 *
+	 */
+
 	/*
 	 * Add flags for dependency generation only to the preprocessor command line.
 	 */
@@ -2504,10 +3014,12 @@ cc_reset(void)
 	args_free(orig_args); orig_args = NULL;
 	free(input_file); input_file = NULL;
 	free(output_obj); output_obj = NULL;
+	if (output_dwo) free(output_dwo); output_dwo = NULL;
 	free(output_dep); output_dep = NULL;
 	free(output_dia); output_dia = NULL;
 	free(cached_obj_hash); cached_obj_hash = NULL;
 	free(cached_obj); cached_obj = NULL;
+	if (cached_dwo) free(cached_dwo); cached_dwo = NULL;
 	free(cached_stderr); cached_stderr = NULL;
 	free(cached_dep); cached_dep = NULL;
 	free(cached_dia); cached_dia = NULL;
@@ -2524,6 +3036,7 @@ cc_reset(void)
 	output_is_precompiled_header = false;
 
 	conf = conf_create();
+	split_dwarf_p = false;
 }
 
 /* Make a copy of stderr that will not be cached, so things like
@@ -2619,7 +3132,33 @@ ccache(int argc, char *argv[])
 	if (output_dia) {
 		cc_log("Diagnostic file: %s", output_dia);
 	}
-	cc_log("Object file: %s", output_obj);
+
+	/*
+	 * Note: cc_process_args ought to have generated output_dwo.  But we
+	 * may not want to do so before generating dependencies because it has
+	 * been the implicit ordering that the dependency is generated first
+	 * and then object file is generated.
+	 * See a block comment that starts with
+	 * "-gsplit-dwarf support: Ordering of dependency generation."
+	 * in the earlier part of this file.
+	 */
+
+	if (split_dwarf_p ) {
+		if (output_dia)
+			cc_log("output_dia = %s", output_dia);
+		if (output_dwo)
+			cc_log("output_dwo = %s", output_dwo);
+		fflush(stdout);
+		if (!generating_dependencies)
+			assert (output_dwo);
+	} else {
+		assert (!output_dwo);
+	}
+
+	if (!generating_dependencies && output_dwo) {
+		cc_log("Split dwarf file: %s", output_dwo);
+	}
+	cc_log("(output_obj) Object file: %s", output_obj);
 
 	hash_start(&common_hash);
 	calculate_common_hash(preprocessor_args, &common_hash);
@@ -2775,7 +3314,7 @@ ccache_main_options(int argc, char *argv
 				initialize();
 				files = atoi(optarg);
 				if (conf_set_value_in_file(primary_config_path, "max_files", optarg,
-				                           &errmsg)) {
+							   &errmsg)) {
 					if (files == 0) {
 						printf("Unset cache file limit\n");
 					} else {
@@ -2795,7 +3334,7 @@ ccache_main_options(int argc, char *argv
 					fatal("invalid size: %s", optarg);
 				}
 				if (conf_set_value_in_file(primary_config_path, "max_size", optarg,
-				                           &errmsg)) {
+							   &errmsg)) {
 					if (size == 0) {
 						printf("Unset cache size limit\n");
 					} else {
Only in ccache-gsplit-dwarf-support: ccache.c.saved
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/compopt.c ccache-gsplit-dwarf-support/compopt.c
--- ccache/compopt.c	2014-12-26 00:16:41.857924683 +0900
+++ ccache-gsplit-dwarf-support/compopt.c	2014-10-31 01:23:27.861419530 +0900
@@ -60,7 +60,6 @@ static const struct compopt compopts[] =
 	{"-frepo",          TOO_HARD},
 	{"-ftest-coverage", TOO_HARD}, /* generates a .gcno file at the same time */
 	{"-fworking-directory", AFFECTS_CPP},
-	{"-gsplit-dwarf",   TOO_HARD}, /* generates a .dwo file at the same time */
 	{"-idirafter",      AFFECTS_CPP | TAKES_ARG | TAKES_PATH},
 	{"-iframework",     AFFECTS_CPP | TAKES_ARG | TAKES_CONCAT_ARG | TAKES_PATH},
 	{"-imacros",        AFFECTS_CPP | TAKES_ARG | TAKES_PATH},
Only in ccache-gsplit-dwarf-support: do-diff.sh
Only in ccache-gsplit-dwarf-support: do-test-split-dwarf.sh
Only in ccache-gsplit-dwarf-support: do-test.sh
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/execute.c ccache-gsplit-dwarf-support/execute.c
--- ccache/execute.c	2015-03-04 23:01:48.149927458 +0900
+++ ccache-gsplit-dwarf-support/execute.c	2015-03-04 22:59:49.424081775 +0900
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) Andrew Tridgell 2002
- * Copyright (C) Joel Rosdahl 2011
+ * Copyright (C) Joel Rosdahl 2011-2015
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
@@ -174,7 +174,7 @@ win32execute(char *path, char **argv, in
 	char full_path_win_ext[MAX_PATH] = {0};
 	add_exe_ext_if_no_to_fullpath(full_path_win_ext, MAX_PATH, ext, path);
 	ret = CreateProcess(full_path_win_ext, args, NULL, NULL, 1, 0, NULL, NULL,
-	                    &si, &pi);
+			    &si, &pi);
 	if (fd_stdout != -1) {
 		close(fd_stdout);
 		close(fd_stderr);
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/hash.c ccache-gsplit-dwarf-support/hash.c
--- ccache/hash.c	2014-12-26 00:16:41.857924683 +0900
+++ ccache-gsplit-dwarf-support/hash.c	2015-03-04 03:36:51.011393317 +0900
@@ -128,6 +128,7 @@ hash_file(struct mdfour *md, const char
 
 	fd = open(fname, O_RDONLY|O_BINARY);
 	if (fd == -1) {
+		cc_log("hash file creation (%s) failed\n", fname); /* to catch strange errors */
 		return false;
 	}
 
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/language.c ccache-gsplit-dwarf-support/language.c
--- ccache/language.c	2014-12-26 00:16:41.857924683 +0900
+++ ccache-gsplit-dwarf-support/language.c	2015-03-04 22:59:49.424081775 +0900
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010, 2013 Joel Rosdahl
+ * Copyright (C) 2010-2015 Joel Rosdahl
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
@@ -147,7 +147,7 @@ extension_for_language(const char *langu
 bool
 language_is_supported(const char *language)
 {
-	return p_language_for_language(language);
+	return p_language_for_language(language) != NULL;
 }
 
 bool
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/manifest.c ccache-gsplit-dwarf-support/manifest.c
--- ccache/manifest.c	2014-12-26 00:16:41.857924683 +0900
+++ ccache-gsplit-dwarf-support/manifest.c	2015-03-04 22:59:49.424081775 +0900
@@ -598,11 +598,31 @@ add_object_entry(struct manifest *mf,
 	obj = &mf->objects[n];
 
 	n = hashtable_count(included_files);
+#if defined(CI_DEBUG)
+	{
+		char tmpbuf[128];
+		snprintf(tmpbuf, 128, "add_object_entry: hashtable_count = %d", n);
+		cc_log(tmpbuf);
+        }
+#endif
+
 	obj->n_file_info_indexes = n;
 	obj->file_info_indexes = x_malloc(n * sizeof(*obj->file_info_indexes));
 	add_file_info_indexes(obj->file_info_indexes, n, mf, included_files);
 	memcpy(obj->hash.hash, object_hash->hash, mf->hash_size);
 	obj->hash.size = object_hash->size;
+#if defined(CI_DEBUG)
+	{
+		int i;
+		static char tmpbuf[1024];
+		unsigned char *cp = (unsigned char *) obj->hash.hash ;
+		n = snprintf(tmpbuf, 1024,"add_object_entry: ");
+		for(i = 0; i < mf->hash_size; i++)
+			snprintf(&tmpbuf[n+i*2], 1024 - n - i * 2, "%02x", cp[i]);
+		snprintf(&tmpbuf[1024 - n - i * 2 + 2], 1024, "\n");
+		cc_log(tmpbuf);
+	}
+#endif
 }
 
 /*
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/stats.c ccache-gsplit-dwarf-support/stats.c
--- ccache/stats.c	2014-12-14 03:46:53.071511757 +0900
+++ ccache-gsplit-dwarf-support/stats.c	2014-12-14 03:55:46.450168960 +0900
@@ -374,7 +374,7 @@ stats_zero(void)
 /* Get the per directory limits */
 void
 stats_get_obsolete_limits(const char *dir, unsigned *maxfiles,
-                          uint64_t *maxsize)
+			  uint64_t *maxsize)
 {
 	struct counters *counters = counters_init(STATS_END);
 	char *sname = format("%s/stats", dir);
Only in ccache/test: main
Only in ccache-gsplit-dwarf-support: test-file-1.c
Only in ccache-gsplit-dwarf-support: test-file-2.c
Only in ccache-gsplit-dwarf-support: test-file-2.s
Only in ccache: testdir.18714
Only in ccache: testdir.19069
Only in ccache: testdir.20915
Only in ccache: testdir.2264
Only in ccache-gsplit-dwarf-support: testdir.3089
Only in ccache-gsplit-dwarf-support: testdir.865
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/util.c ccache-gsplit-dwarf-support/util.c
--- ccache/util.c	2015-03-04 23:01:48.153927399 +0900
+++ ccache-gsplit-dwarf-support/util.c	2015-03-06 01:37:58.201687462 +0900
@@ -108,15 +108,27 @@ path_max(const char *path)
 }
 
 static void
+warn_log_fail() {
+	fprintf(stderr,
+		"Writing to logfile failed.\n"
+		"Check the permission and make sure there is enough room for writing to the filesystem.\n");
+	/* maybe we should exit here? */
+}
+
+static void
 vlog(const char *format, va_list ap, bool log_updated_time)
 {
+	int rc1, rc2;
 	if (!init_log()) {
 		return;
 	}
 
 	log_prefix(log_updated_time);
-	vfprintf(logfile, format, ap);
-	fprintf(logfile, "\n");
+	rc1 = vfprintf(logfile, format, ap);
+	rc2 = fprintf(logfile, "\n");
+	if (rc1 < 0 || rc2 < 0) {
+		warn_log_fail();
+	}
 }
 
 /*
@@ -153,6 +165,7 @@ cc_bulklog(const char *format, ...)
 void
 cc_log_argv(const char *prefix, char **argv)
 {
+	int rc;
 	if (!init_log()) {
 		return;
 	}
@@ -160,7 +173,9 @@ cc_log_argv(const char *prefix, char **a
 	log_prefix(true);
 	fputs(prefix, logfile);
 	print_command(logfile, argv);
-	fflush(logfile);
+	rc = fflush(logfile);
+	if (rc)
+		warn_log_fail();
 }
 
 /* something went badly wrong! */
@@ -827,7 +842,7 @@ traverse(const char *dir, void (*fn)(con
 		fname = format("%s/%s", dir, de->d_name);
 		if (lstat(fname, &st)) {
 			if (errno != ENOENT) {
-				perror(fname);
+				cc_log("lstat on file %s failed.", fname);
 			}
 			free(fname);
 			continue;
@@ -1413,8 +1428,14 @@ x_rename(const char *oldpath, const char
 int
 tmp_unlink(const char *path)
 {
-	cc_log("Unlink %s", path);
-	return unlink(path);
+	/* verbose for debugging -gsplit-dwarf */
+	int rc;
+	cc_log("tmp_unlink:Unlink %s", path);
+	rc = unlink(path);
+	if (rc) {
+		cc_log("tmp_unlink:Unlink failed: rc = %d", rc);
+	}
+	return rc;
 }
 
 /*
@@ -1430,7 +1451,7 @@ x_unlink(const char *path)
 	 */
 	char *tmp_name = format("%s.rm.%s", path, tmp_string());
 	int result = 0;
-	cc_log("Unlink %s via %s", path, tmp_name);
+	cc_log("x_unlink: Unlink %s via %s", path, tmp_name);
 	if (x_rename(path, tmp_name) == -1) {
 		result = -1;
 		goto out;
@@ -1443,6 +1464,10 @@ x_unlink(const char *path)
 	}
 out:
 	free(tmp_name);
+	if (result) {
+		/* verbose for debugging -gsplit-dwarf */
+		cc_log("x_unlink: failed result = %d", result);
+	}
 	return result;
 }
 
diff '--exclude=test.sh' '--exclude=*.log' '--exclude=*.o' '--exclude=.gitignore' '--exclude=config.status' '--exclude=autom4te.cache' '--exclude=.deps' '--exclude=.git' '--exclude=*.txt' '--exclude=*.in' '--exclude=Makefile*' -p -ur ccache/version.c ccache-gsplit-dwarf-support/version.c
--- ccache/version.c	2014-12-26 00:10:38.346977900 +0900
+++ ccache-gsplit-dwarf-support/version.c	2015-03-06 01:39:45.213097200 +0900
@@ -1 +1 @@
-const char CCACHE_VERSION[] = "3.2.1+1_g090af0a";
+const char CCACHE_VERSION[] = "3.1.9+361_gc38c67e_dirty";