From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756591AbcJWQrS (ORCPT ); Sun, 23 Oct 2016 12:47:18 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34394 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755617AbcJWQrQ (ORCPT ); Sun, 23 Oct 2016 12:47:16 -0400 Subject: Re: [PATCH v2 1/1] x86, relocs: add function attributes to die() To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86 References: <173b263e-76ff-c8c9-aff8-ee6097164f4c@m4x.org> <20160904165101.15596-1-nicolas.iooss_linux@m4x.org> Cc: Nilay Vaish , Linux Kernel list From: Nicolas Iooss Message-ID: <313ea0be-956e-def9-839c-23e991f92829@m4x.org> Date: Sun, 23 Oct 2016 18:47:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, A few weeks ago I sent the patch below and got a review, but this patch has not been applied yet in linux-next. Does it cause a problem I need to fix? Thanks, Nicolas On 05/09/16 17:28, Nilay Vaish wrote: > On 4 September 2016 at 11:51, Nicolas Iooss 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 >> --- >> 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 >> #include >> >> -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 >