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

Luca Boccassi
2020-12-17T19:27:06Z

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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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