[PATCH] perf stat: Fix s390x compile error on F32 utils/stat-display.c

Thomas Richter
2020-08-25T06:33:15Z

Fix a compile error on F32 and gcc version 10.1 on s390 in file
utils/stat-display.c. The error does not show up with make DEBUG=y.
In fact the issue shows up when using both compiler options
-O6 and -D_FORTIFY_SOURCE=2 (which are omitted with DEBUG=Y).

This is the offending call chain:
print_counter_aggr()
printout(config, -1, 0, ...) with 2nd parm id set to -1
aggr_printout(config, x, id --> -1, ...) which leads to this code:
case AGGR_NONE:
if (evsel->percore && !config->percore_show_thread) {
....
} else {
fprintf(config->output, "CPU%*d%s",
config->csv_output ? 0 : -7,
evsel__cpus(evsel)->map[id],
^^ id is -1 !!!!
config->csv_sep);
}

This is a compiler inlining issue which is detected on s390 but not on
other plattforms.

Output before:
# make util/stat-display.o
.....

util/stat-display.c: In function ‘perf_evlist__print_counters’:
util/stat-display.c:121:4: error: array subscript -1 is below array
bounds of ‘int[]’ [-Werror=array-bounds]
121 | fprintf(config->output, "CPU%*d%s",
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
122 | config->csv_output ? 0 : -7,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
123 | evsel__cpus(evsel)->map[id],
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
124 | config->csv_sep);
| ~~~~~~~~~~~~~~~~
In file included from util/evsel.h:13,
from util/evlist.h:13,
from util/stat-display.c:9:
/root/linux/tools/lib/perf/include/internal/cpumap.h:10:7:
note: while referencing ‘map’
10 | int map[];
| ^~~
cc1: all warnings being treated as errors
mv: cannot stat 'util/.stat-display.o.tmp': No such file or directory
make[3]: *** [/root/linux/tools/build/Makefile.build:97: util/stat-display.o]
Error 1
make[2]: *** [Makefile.perf:716: util/stat-display.o] Error 2
make[1]: *** [Makefile.perf:231: sub-make] Error 2
make: *** [Makefile:110: util/stat-display.o] Error 2
[root@t35lp46 perf]#

Output after:
# make util/stat-display.o
.....
CC util/stat-display.o
[root@t35lp46 perf]#

Suggested-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
tools/perf/util/stat-display.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index 57d0706e1330..cbe836649f84 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -117,12 +117,11 @@ static void aggr_printout(struct perf_stat_config *config,
cpu_map__id_to_die(id),
config->csv_output ? 0 : -3,
cpu_map__id_to_cpu(id), config->csv_sep);
- } else {
+ } else if (id > -1)
fprintf(config->output, "CPU%*d%s",
config->csv_output ? 0 : -7,
evsel__cpus(evsel)->map[id],
config->csv_sep);
- }
break;
case AGGR_THREAD:
fprintf(config->output, "%*s-%*d%s",
--
2.26.2