linux-kernel - [PATCH] perf: fix -Wstring-compare

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Date:   Sun, 23 Feb 2020 11:34:49 -0800
From:   Nick Desaulniers <nick.desaulniers@...il.com>
To:     acme@...nel.org, mingo@...hat.com, peterz@...radead.org
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <nick.desaulniers@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Changbin Du <changbin.du@...el.com>,
        John Keeping <john@...anate.com>,
        Song Liu <songliubraving@...com>, linux-kernel@...r.kernel.org
Subject: [PATCH] perf: fix -Wstring-compare

Clang warns:

util/block-info.c:298:18: error: result of comparison against a string
literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                        ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:51: error: result of comparison against a string
literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                         ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:18: error: result of comparison against a string
literal is unspecified (use an explicit string
comparison function instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                        ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:51: error: result of comparison against a string
literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                         ^  ~~~~~~~~~~~~~~~
util/map.c:434:15: error: result of comparison against a string literal
is unspecified (use an explicit string comparison function instead)
[-Werror,-Wstring-compare]
                if (srcline != SRCLINE_UNKNOWN)
                            ^  ~~~~~~~~~~~~~~~

Link: https://github.com/ClangBuiltLinux/linux/issues/900
Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
---
Note: was generated off of mainline; can rebase on -next if it doesn't
apply cleanly.


 tools/perf/builtin-diff.c    | 3 ++-
 tools/perf/util/block-info.c | 3 ++-
 tools/perf/util/map.c        | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index f8b6ae557d8b..c03c36fde7e2 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -1312,7 +1312,8 @@ static int cycles_printf(struct hist_entry *he, struct hist_entry *pair,
 	end_line = map__srcline(he->ms.map, bi->sym->start + bi->end,
 				he->ms.sym);
 
-	if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
+	if ((strncmp(start_line, SRCLINE_UNKNOWN, strlen(SRCLINE_UNKNOWN)) != 0) &&
+	    (strncmp(end_line, SRCLINE_UNKNOWN, strlen(SRCLINE_UNKNOWN)) != 0)) {
 		scnprintf(buf, sizeof(buf), "[%s -> %s] %4ld",
 			  start_line, end_line, block_he->diff.cycles);
 	} else {
diff --git a/tools/perf/util/block-info.c b/tools/perf/util/block-info.c
index c4b030bf6ec2..fbbb6d640dad 100644
--- a/tools/perf/util/block-info.c
+++ b/tools/perf/util/block-info.c
@@ -295,7 +295,8 @@ static int block_range_entry(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
 	end_line = map__srcline(he->ms.map, bi->sym->start + bi->end,
 				he->ms.sym);
 
-	if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
+	if ((strncmp(start_line, SRCLINE_UNKNOWN, strlen(SRCLINE_UNKNOWN)) != 0) &&
+	    (strncmp(end_line, SRCLINE_UNKNOWN, strlen(SRCLINE_UNKNOWN)) != 0)) {
 		scnprintf(buf, sizeof(buf), "[%s -> %s]",
 			  start_line, end_line);
 	} else {
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index a08ca276098e..95428511300d 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -431,7 +431,7 @@ int map__fprintf_srcline(struct map *map, u64 addr, const char *prefix,
 
 	if (map && map->dso) {
 		char *srcline = map__srcline(map, addr, NULL);
-		if (srcline != SRCLINE_UNKNOWN)
+		if (strncmp(srcline, SRCLINE_UNKNOWN, strlen(SRCLINE_UNKNOWN)) != 0)
 			ret = fprintf(fp, "%s%s", prefix, srcline);
 		free_srcline(srcline);
 	}
-- 
2.17.1