Re: [fsverity-utils PATCH v2 2/2] Allow to build and run sign/digest on Windows

[Luca Boccassi <luca.boccassi@gmail.com>]

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On Thu, 2020-12-17 at 11:20 -0800, Eric Biggers wrote:
> On Thu, Dec 17, 2020 at 07:12:06PM +0000, Luca Boccassi wrote:
> > I get the following warning with the mingw build now:
> > 
> > lib/utils.c: In function ‘xmalloc’:
> > lib/utils.c:23:25: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 2 has type ‘size_t’ {aka ‘long long unsigned int’} [-Wformat=]
> >    libfsverity_error_msg("out of memory (tried to allocate %" SIZET_PF " bytes)",
> >                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >            size);
> >            ~~~~           
> > In file included from lib/../common/win32_defs.h:24,
> >                  from lib/../common/common_defs.h:18,
> >                  from lib/lib_private.h:15,
> >                  from lib/utils.c:12:
> > /usr/share/mingw-w64/include/inttypes.h:94:20: note: format string is defined here
> >  #define PRIu64 "I64u"
> >   AR       libfsverity.a
> >   CC       lib/sign_digest.shlib.o
> >   CC       lib/compute_digest.shlib.o
> >   CC       lib/hash_algs.shlib.o
> >   CC       lib/utils.shlib.o
> > lib/utils.c: In function ‘xmalloc’:
> > lib/utils.c:23:25: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 2 has type ‘size_t’ {aka ‘long long unsigned int’} [-Wformat=]
> >    libfsverity_error_msg("out of memory (tried to allocate %" SIZET_PF " bytes)",
> >                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >            size);
> >            ~~~~           
> > In file included from lib/../common/win32_defs.h:24,
> >                  from lib/../common/common_defs.h:18,
> >                  from lib/lib_private.h:15,
> >                  from lib/utils.c:12:
> > /usr/share/mingw-w64/include/inttypes.h:94:20: note: format string is defined here
> >  #define PRIu64 "I64u"
> > 
> > 
> > But, honestly, it seems harmless to me. If someone on Windows is trying
> > to get a digest and don't have memory to do it, they'll have bigger
> > problems to worry about than knowing how much it was requested. I'll
> > send a v3 with your suggested changes. As far as I can read online,
> > handling %zu in a cross compatible way is like the number one
> > annoyance.
> > 
> 
> It needs to compile without warnings, otherwise new warnings won't be noticed.
> 
> I think that if the MinGW printf is used (by defining _GNU_SOURCE), then %zu
> would just work as-is.  That's what I do in another project.  Try:
> 
> diff --git a/Makefile b/Makefile
> index cc62818..44aee92 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -52,7 +52,7 @@ override CFLAGS := -Wall -Wundef				\
>  	$(call cc-option,-Wvla)					\
>  	$(CFLAGS)
>  
> -override CPPFLAGS := -Iinclude -D_FILE_OFFSET_BITS=64 $(CPPFLAGS)
> +override CPPFLAGS := -Iinclude -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE $(CPPFLAGS)
>  
>  ifneq ($(V),1)
>  QUIET_CC        = @echo '  CC      ' $@;
> diff --git a/common/win32_defs.h b/common/win32_defs.h
> index e13938a..3b0d908 100644
> --- a/common/win32_defs.h
> +++ b/common/win32_defs.h
> @@ -23,12 +23,6 @@
>  #include <stdint.h>
>  #include <inttypes.h>
>  
> -#ifdef _WIN64
> -#  define SIZET_PF PRIu64
> -#else
> -#  define SIZET_PF PRIu32
> -#endif
> -
>  #ifndef ENOPKG
>  #   define ENOPKG 65
>  #endif
> @@ -37,6 +31,11 @@
>  #  define __cold
>  #endif
>  
> +#ifndef __printf
> +#  define __printf(fmt_idx, vargs_idx) \
> +	__attribute__((format(gnu_printf, fmt_idx, vargs_idx)))
> +#endif
> +
>  typedef __signed__ char __s8;
>  typedef unsigned char __u8;
>  typedef __signed__ short __s16;
> @@ -52,10 +51,6 @@ typedef __u32 __be32;
>  typedef __u64 __le64;
>  typedef __u64 __be64;
>  
> -#else
> -
> -#define SIZET_PF "zu"
> -
>  #endif /* _WIN32 */
>  
>  #endif /* COMMON_WIN32_DEFS_H */
> diff --git a/lib/utils.c b/lib/utils.c
> index 8bb4413..036dd60 100644
> --- a/lib/utils.c
> +++ b/lib/utils.c
> @@ -9,8 +9,6 @@
>   * https://opensource.org/licenses/MIT.
>   */
>  
> -#define _GNU_SOURCE /* for asprintf() and strerror_r() */
> -
>  #include "lib_private.h"
>  
>  #include <stdio.h>
> @@ -22,7 +20,7 @@ static void *xmalloc(size_t size)
>  	void *p = malloc(size);
>  
>  	if (!p)
> -		libfsverity_error_msg("out of memory (tried to allocate %" SIZET_PF " bytes)",
> +		libfsverity_error_msg("out of memory (tried to allocate %zu bytes)",
>  				      size);
>  	return p;
>  }

That works, no more warnings, nice! Thank you! Sent v4.

-- 
Kind regards,
Luca Boccassi

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