Merge branch 'en/assert-wo-side-effects'

Ensure what we write in assert() does not have side effects,
and introduce ASSERT() macro to mark those that cannot be
mechanically checked for lack of side effects.

* en/assert-wo-side-effects:
  treewide: replace assert() with ASSERT() in special cases
  ci: add build checking for side-effects in assert() calls
  git-compat-util: introduce ASSERT() macro

Author: gitster

Makefile

@@ -2263,6 +2263,10 @@ ifdef WITH_BREAKING_CHANGES
 	BASIC_CFLAGS += -DWITH_BREAKING_CHANGES
 endif
 
+ifdef CHECK_ASSERTION_SIDE_EFFECTS
+	BASIC_CFLAGS += -DCHECK_ASSERTION_SIDE_EFFECTS
+endif
+
 ifdef INCLUDE_LIBGIT_RS
 	# Enable symbol hiding in contrib/libgit-sys/libgitpub.a without making
 	# us rebuild the whole tree every time we run a Rust build.

ci/check-unsafe-assertions.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+make CHECK_ASSERTION_SIDE_EFFECTS=1 >compiler_output 2>compiler_error
+if test $? != 0
+then
+	echo >&2 "ERROR: The compiler could not verify the following assert()"
+	echo >&2 "       calls are free of side-effects.  Please replace with"
+	echo >&2 "       ASSERT() calls."
+	grep undefined.reference.to..not_supposed_to_survive compiler_error |
+		sed -e s/:[^:]*$// | sort | uniq | tr ':' ' ' |
+		while read f l
+		do
+			printf "${f}:${l}\n  "
+			awk -v start="$l" 'NR >= start { print; if (/\);/) exit }' $f
+		done
+	exit 1
+fi
+rm compiler_output compiler_error

ci/run-static-analysis.sh

@@ -31,4 +31,6 @@ exit 1
 
 make check-pot
 
+${0%/*}/check-unsafe-assertions.sh
+
 save_good_tree

diffcore-rename.c

@@ -1406,7 +1406,7 @@ void diffcore_rename_extended(struct diff_options *options,
 
 	trace2_region_enter("diff", "setup", options->repo);
 	info.setup = 0;
-	assert(!dir_rename_count || strmap_empty(dir_rename_count));
+	ASSERT(!dir_rename_count || strmap_empty(dir_rename_count));
 	want_copies = (detect_rename == DIFF_DETECT_COPY);
 	if (dirs_removed && (break_idx || want_copies))
 		BUG("dirs_removed incompatible with break/copy detection");

git-compat-util.h

@@ -1460,6 +1460,8 @@ extern int bug_called_must_BUG;
 __attribute__((format (printf, 3, 4))) NORETURN
 void BUG_fl(const char *file, int line, const char *fmt, ...);
 #define BUG(...) BUG_fl(__FILE__, __LINE__, __VA_ARGS__)
+/* ASSERT: like assert(), but won't be compiled out with NDEBUG */
+#define ASSERT(a) if (!(a)) BUG("Assertion `" #a "' failed.")
 __attribute__((format (printf, 3, 4)))
 void bug_fl(const char *file, int line, const char *fmt, ...);
 #define bug(...) bug_fl(__FILE__, __LINE__, __VA_ARGS__)
@@ -1592,4 +1594,11 @@ static inline void *container_of_or_null_offset(void *ptr, size_t offset)
  */
 #define NOT_CONSTANT(expr) ((expr) || false_but_the_compiler_does_not_know_it_)
 extern int false_but_the_compiler_does_not_know_it_;
+
+#ifdef CHECK_ASSERTION_SIDE_EFFECTS
+#undef assert
+extern int not_supposed_to_survive;
+#define assert(expr) ((void)(not_supposed_to_survive || (expr)))
+#endif /* CHECK_ASSERTION_SIDE_EFFECTS */
+
 #endif

merge-ort.c

@@ -791,7 +791,7 @@ static void path_msg(struct merge_options *opt,
 	struct strbuf tmp = STRBUF_INIT;
 
 	/* Sanity checks */
-	assert(omittable_hint ==
+	ASSERT(omittable_hint ==
 	       (!starts_with(type_short_descriptions[type], "CONFLICT") &&
 		!starts_with(type_short_descriptions[type], "ERROR")) ||
 	       type == CONFLICT_DIR_RENAME_SUGGESTED);
@@ -1642,7 +1642,7 @@ static int handle_deferred_entries(struct merge_options *opt,
 			ci = strmap_get(&opt->priv->paths, path);
 			VERIFY_CI(ci);
 
-			assert(renames->deferred[side].trivial_merges_okay &&
+			ASSERT(renames->deferred[side].trivial_merges_okay &&
 			       !strset_contains(&renames->deferred[side].target_dirs,
 						path));
 			resolve_trivial_directory_merge(ci, side);

merge-recursive.c

@@ -1197,7 +1197,7 @@ static void print_commit(struct repository *repo, struct commit *commit)
 	struct pretty_print_context ctx = {0};
 	ctx.date_mode.type = DATE_NORMAL;
 	/* FIXME: Merge this with output_commit_title() */
-	assert(!merge_remote_util(commit));
+	ASSERT(!merge_remote_util(commit));
 	repo_format_commit_message(repo, commit, " %h: %m %s", &sb, &ctx);
 	fprintf(stderr, "%s\n", sb.buf);
 	strbuf_release(&sb);

object-file.c

@@ -2706,7 +2706,7 @@ static int index_stream_convert_blob(struct index_state *istate,
 	struct strbuf sbuf = STRBUF_INIT;
 
 	assert(path);
-	assert(would_convert_to_git_filter_fd(istate, path));
+	ASSERT(would_convert_to_git_filter_fd(istate, path));
 
 	convert_to_git_filter_fd(istate, path, fd, &sbuf,
 				 get_conv_flags(flags));

parallel-checkout.c

@@ -277,7 +277,7 @@ static int write_pc_item_to_fd(struct parallel_checkout_item *pc_item, int fd,
 	ssize_t wrote;
 
 	/* Sanity check */
-	assert(is_eligible_for_parallel_checkout(pc_item->ce, &pc_item->ca));
+	ASSERT(is_eligible_for_parallel_checkout(pc_item->ce, &pc_item->ca));
 
 	filter = get_stream_filter_ca(&pc_item->ca, &pc_item->ce->oid);
 	if (filter) {

scalar.c

@@ -241,7 +241,7 @@ static int add_or_remove_enlistment(int add)
 
 static int start_fsmonitor_daemon(void)
 {
-	assert(have_fsmonitor_support());
+	ASSERT(have_fsmonitor_support());
 
 	if (fsmonitor_ipc__get_state() != IPC_STATE__LISTENING)
 		return run_git("fsmonitor--daemon", "start", NULL);
@@ -251,7 +251,7 @@ static int start_fsmonitor_daemon(void)
 
 static int stop_fsmonitor_daemon(void)
 {
-	assert(have_fsmonitor_support());
+	ASSERT(have_fsmonitor_support());
 
 	if (fsmonitor_ipc__get_state() == IPC_STATE__LISTENING)
 		return run_git("fsmonitor--daemon", "stop", NULL);