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SubjectRe: [PATCH v2] perf tools: Fix arm64 build error with gcc-11
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On 10/02/2021 03:24, Jianlin Lv wrote:
> gcc version: 11.0.0 20210208 (experimental) (GCC)
>
> Following build error on arm64:
>
> .......
> In function ‘printf’,
> inlined from ‘regs_dump__printf’ at util/session.c:1141:3,
> inlined from ‘regs__printf’ at util/session.c:1169:2:
> /usr/include/aarch64-linux-gnu/bits/stdio2.h:107:10: \
> error: ‘%-5s’ directive argument is null [-Werror=format-overflow=]
>
> 107 | return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, \
> __va_arg_pack ());
>
> ......
> In function ‘fprintf’,
> inlined from ‘perf_sample__fprintf_regs.isra’ at \
> builtin-script.c:622:14:
> /usr/include/aarch64-linux-gnu/bits/stdio2.h:100:10: \
> error: ‘%5s’ directive argument is null [-Werror=format-overflow=]
> 100 | return __fprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt,
> 101 | __va_arg_pack ());
>
> cc1: all warnings being treated as errors
> .......
>
> This patch fixes Wformat-overflow warnings. Add ternary operator,
> The statement evaluates to "Unknown" if reg_name==NULL is met.
>
> Signed-off-by: Jianlin Lv <Jianlin.Lv@arm.com>
> ---
> v2: Add ternary operator to avoid similar errors in other arch.
> ---
> tools/perf/builtin-script.c | 4 +++-
> tools/perf/util/scripting-engines/trace-event-python.c | 4 +++-
> tools/perf/util/session.c | 5 +++--
> 3 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index 42dad4a0f8cf..d59da3a063d0 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -635,6 +635,7 @@ static int perf_sample__fprintf_regs(struct regs_dump *regs, uint64_t mask,
> {
> unsigned i = 0, r;
> int printed = 0;
> + const char *reg_name;
>
> if (!regs || !regs->regs)
> return 0;
> @@ -643,7 +644,8 @@ static int perf_sample__fprintf_regs(struct regs_dump *regs, uint64_t mask,
>
> for_each_set_bit(r, (unsigned long *) &mask, sizeof(mask) * 8) {
> u64 val = regs->regs[i++];
> - printed += fprintf(fp, "%5s:0x%"PRIx64" ", perf_reg_name(r), val);
> + reg_name = perf_reg_name(r);
> + printed += fprintf(fp, "%5s:0x%"PRIx64" ", reg_name ?: "Unknown", val);

is it possible not have to do this check for NULL and reassignment
everywhere?

> }
>
> return printed;
> diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
> index c83c2c6564e0..e1222cc6a699 100644
> --- a/tools/perf/util/scripting-engines/trace-event-python.c
> +++ b/tools/perf/util/scripting-engines/trace-event-python.c
> @@ -691,6 +691,7 @@ static int regs_map(struct regs_dump *regs, uint64_t mask, char *bf, int size)
> {
> unsigned int i = 0, r;
> int printed = 0;
> + const char *reg_name;
>
> bf[0] = 0;
>
> @@ -700,9 +701,10 @@ static int regs_map(struct regs_dump *regs, uint64_t mask, char *bf, int size)
> for_each_set_bit(r, (unsigned long *) &mask, sizeof(mask) * 8) {

a good practice is to limit scope of variables as much as possible, so
reg_name could be declared here

> u64 val = regs->regs[i++];
>
> + reg_name = perf_reg_name(r);
> printed += scnprintf(bf + printed, size - printed,
> "%5s:0x%" PRIx64 " ",
> - perf_reg_name(r), val);
> + reg_name ?: "Unknown", val);
> }
>
> return printed;
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 25adbcce0281..1058d8487e98 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1135,12 +1135,13 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
> static void regs_dump__printf(u64 mask, u64 *regs)
> {
> unsigned rid, i = 0;
> + const char *reg_name;
>
> for_each_set_bit(rid, (unsigned long *) &mask, sizeof(mask) * 8) {
> u64 val = regs[i++];
> -
> + reg_name = perf_reg_name(rid);
> printf(".... %-5s 0x%016" PRIx64 "\n",
> - perf_reg_name(rid), val);
> + reg_name ?: "Unknown", val);

super nit: it's "unknown" in util/perf_regs.h::perf_reg_name(), so nice
to be consistent


> }
> }
>
>

thanks,
John

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