Messages in this thread | | | From | Nilay Vaish <> | Date | Mon, 5 Sep 2016 10:28:56 -0500 | Subject | Re: [PATCH v2 1/1] x86, relocs: add function attributes to die() |
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On 4 September 2016 at 11:51, Nicolas Iooss <nicolas.iooss_linux@m4x.org> wrote: > When building the kernel with clang and some warning flags, the compiler > reports the following warning: > > arch/x86/tools/relocs.c:979:6: warning: variable 'do_reloc' is used > uninitialized whenever 'if' condition is false > [-Wsometimes-uninitialized] > if (!use_real_mode) > ^~~~~~~~~~~~~~ > arch/x86/tools/relocs.c:991:14: note: uninitialized use occurs here > walk_relocs(do_reloc); > ^~~~~~~~ > arch/x86/tools/relocs.c:979:2: note: remove the 'if' if its > condition is always true > if (!use_real_mode) > ^~~~~~~~~~~~~~~~~~~ > arch/x86/tools/relocs.c:976:24: note: initialize the variable > 'do_reloc' to silence this warning > const char *symname); > ^ > = NULL > > This is obviously a false positive: whenever the 'if' condition is > false, the program calls die(). Nevertheless the compiler did not know > this call makes the program quit because this function did not have a > noreturn attribute. Add it. > > While at it, add a printf attribute too to die() and constify the format > parameter. This leads to some errors when compiling on x86_64: > > arch/x86/tools/relocs.c:460:5: error: format specifies type 'int' > but the argument has type 'Elf64_Xword' (aka 'unsigned long') > [-Werror,-Wformat] > sec->shdr.sh_size); > ^~~~~~~~~~~~~~~~~ > arch/x86/tools/relocs.c:464:5: error: format specifies type 'int' > but the argument has type 'Elf64_Off' (aka 'unsigned long') > [-Werror,-Wformat] > sec->shdr.sh_offset, strerror(errno)); > ^~~~~~~~~~~~~~~~~~~ > > When relocs.c is included by relocs_32.c, sec->shdr.sh_size and > sec->shdr.sh_offset are 32-bit unsigned integers. When the file is > included by relocs_64.c, these expressions are 64-bit unsigned integers. > > Introduce a PRIuELF macro to define the right format to use when > printing these expressions. > > Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org> > --- > arch/x86/tools/relocs.c | 14 +++++++------- > arch/x86/tools/relocs.h | 3 ++- > arch/x86/tools/relocs_32.c | 3 +++ > arch/x86/tools/relocs_64.c | 3 +++ > arch/x86/tools/relocs_common.c | 2 +- > 5 files changed, 16 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c > index 0c2fae8d929d..4cad603b8d58 100644 > --- a/arch/x86/tools/relocs.c > +++ b/arch/x86/tools/relocs.c > @@ -397,7 +397,7 @@ static void read_shdrs(FILE *fp) > ehdr.e_shnum); > } > if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) { > - die("Seek to %d failed: %s\n", > + die("Seek to %"PRIuELF" failed: %s\n", > ehdr.e_shoff, strerror(errno)); > } > for (i = 0; i < ehdr.e_shnum; i++) { > @@ -431,11 +431,11 @@ static void read_strtabs(FILE *fp) > } > sec->strtab = malloc(sec->shdr.sh_size); > if (!sec->strtab) { > - die("malloc of %d bytes for strtab failed\n", > + die("malloc of %"PRIuELF" bytes for strtab failed\n", > sec->shdr.sh_size); > } > if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { > - die("Seek to %d failed: %s\n", > + die("Seek to %"PRIuELF" failed: %s\n", > sec->shdr.sh_offset, strerror(errno)); > } > if (fread(sec->strtab, 1, sec->shdr.sh_size, fp) > @@ -456,11 +456,11 @@ static void read_symtabs(FILE *fp) > } > sec->symtab = malloc(sec->shdr.sh_size); > if (!sec->symtab) { > - die("malloc of %d bytes for symtab failed\n", > + die("malloc of %"PRIuELF" bytes for symtab failed\n", > sec->shdr.sh_size); > } > if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { > - die("Seek to %d failed: %s\n", > + die("Seek to %"PRIuELF" failed: %s\n", > sec->shdr.sh_offset, strerror(errno)); > } > if (fread(sec->symtab, 1, sec->shdr.sh_size, fp) > @@ -489,11 +489,11 @@ static void read_relocs(FILE *fp) > } > sec->reltab = malloc(sec->shdr.sh_size); > if (!sec->reltab) { > - die("malloc of %d bytes for relocs failed\n", > + die("malloc of %"PRIuELF" bytes for relocs failed\n", > sec->shdr.sh_size); > } > if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { > - die("Seek to %d failed: %s\n", > + die("Seek to %"PRIuELF" failed: %s\n", > sec->shdr.sh_offset, strerror(errno)); > } > if (fread(sec->reltab, 1, sec->shdr.sh_size, fp) > diff --git a/arch/x86/tools/relocs.h b/arch/x86/tools/relocs.h > index f59590645b68..6b7969719833 100644 > --- a/arch/x86/tools/relocs.h > +++ b/arch/x86/tools/relocs.h > @@ -16,7 +16,8 @@ > #include <regex.h> > #include <tools/le_byteshift.h> > > -void die(char *fmt, ...); > +__attribute__((format(printf, 1, 2))) __attribute__((noreturn)) > +void die(const char *fmt, ...); > > #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > > diff --git a/arch/x86/tools/relocs_32.c b/arch/x86/tools/relocs_32.c > index b2ade2bb4162..8024ec473e6a 100644 > --- a/arch/x86/tools/relocs_32.c > +++ b/arch/x86/tools/relocs_32.c > @@ -14,4 +14,7 @@ > #define ELF_ST_BIND(o) ELF32_ST_BIND(o) > #define ELF_ST_VISIBILITY(o) ELF32_ST_VISIBILITY(o) > > +/* printf format for Elf32_Off */ > +#define PRIuELF PRIu32 > + > #include "relocs.c" > diff --git a/arch/x86/tools/relocs_64.c b/arch/x86/tools/relocs_64.c > index 56b61b743c4c..2cf4de5c9d99 100644 > --- a/arch/x86/tools/relocs_64.c > +++ b/arch/x86/tools/relocs_64.c > @@ -14,4 +14,7 @@ > #define ELF_ST_BIND(o) ELF64_ST_BIND(o) > #define ELF_ST_VISIBILITY(o) ELF64_ST_VISIBILITY(o) > > +/* printf format for Elf64_Off */ > +#define PRIuELF PRIu64 > + > #include "relocs.c" > diff --git a/arch/x86/tools/relocs_common.c b/arch/x86/tools/relocs_common.c > index acab636bcb34..30adb44eff79 100644 > --- a/arch/x86/tools/relocs_common.c > +++ b/arch/x86/tools/relocs_common.c > @@ -1,6 +1,6 @@ > #include "relocs.h" > > -void die(char *fmt, ...) > +void die(const char *fmt, ...) > { > va_list ap; > va_start(ap, fmt); > -- > 2.9.3 >
I have to admit that this is the first time I am looking at these format specifier macros from inttypes.h. I looked at that file. Your usage seems correct to me and should achieve the desired outcome.
Reviewed-by: Nilay Vaish <nilayvaish@gmail.com>
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