On Tue, Feb 09, 2021 at 02:18:26PM +0000, John Garry wrote: > On 09/02/2021 12:17, Leo Yan wrote: > > Hi Jianlin, > > > > On Tue, Feb 09, 2021 at 07:33:57PM +0800, 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 by replacing the return > > > value NULL of perf_reg_name with "unknown". > > > > > > Signed-off-by: Jianlin Lv <[email protected]> > > > --- > > > tools/perf/arch/arm64/include/perf_regs.h | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/tools/perf/arch/arm64/include/perf_regs.h > > > b/tools/perf/arch/arm64/include/perf_regs.h > > > index baaa5e64a3fb..901419f907c0 100644 > > > --- a/tools/perf/arch/arm64/include/perf_regs.h > > > +++ b/tools/perf/arch/arm64/include/perf_regs.h > > > @@ -85,10 +85,10 @@ static inline const char *perf_reg_name(int id) > > > case PERF_REG_ARM64_PC: > > > return "pc"; > > > default: > > > - return NULL; > > > + return "unknown"; > > > } > > > - return NULL; > > > + return "unknown"; > > > > This issue is a common issue crossing all archs. So it's better to > > change the code in the places where calls perf_reg_name(), e.g. in > > util/session.c: > > > > --- a/tools/perf/util/session.c > > +++ b/tools/perf/util/session.c > > @@ -1135,12 +1135,14 @@ static void branch_stack__printf(struct perf_sample > > *sample, bool callstack) > > static void regs_dump__printf(u64 mask, u64 *regs) > > { > > unsigned rid, i = 0; > > + 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); > > } > > } > > > > And another potential issue is the format specifier "%-5s", it prints > > out maximum to 5 chars, > > Doesn't the width field specify the min, not max, number of characters?
Thanks for correction, John. I wrongly understood it and sorry for confusion. Wiki says [1]: "The Width field specifies a minimum number of characters to output, and is typically used to pad fixed-width fields in tabulated output, where the fields would otherwise be smaller, although it does not cause truncation of oversized fields." Thanks, Leo [1] https://en.wikipedia.org/wiki/Printf_format_string#Width_field
