From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH iproute2] json_print: fix print_uint hidden type promotion Date: Thu, 29 Mar 2018 14:02:37 -0700 Message-ID: <20180329140237.7bb711fc@xeon-e3> References: <20180329192220.30101-1-ldir@darbyshire-bryant.me.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Kevin Darbyshire-Bryant Return-path: Received: from mail-pg0-f67.google.com ([74.125.83.67]:35516 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971AbeC2VCo (ORCPT ); Thu, 29 Mar 2018 17:02:44 -0400 Received: by mail-pg0-f67.google.com with SMTP id j3so3839749pgf.2 for ; Thu, 29 Mar 2018 14:02:44 -0700 (PDT) In-Reply-To: <20180329192220.30101-1-ldir@darbyshire-bryant.me.uk> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 29 Mar 2018 20:22:20 +0100 Kevin Darbyshire-Bryant wrote: > print_int used 'int' type internally, whereas print_uint used 'uint64_t' > > These helper functions eventually call vfprintf(fp, fmt, args) which is > a variable argument list function and is dependent upon 'fmt' containing > correct information about the length of the passed arguments. > > Unfortunately print_int v print_uint offered no clue to the programmer > that internally passed ints to print_uint were being promoted to 64bits, > thus the format passed in 'fmt' string vs the actual passed integer > could be different lengths. This is even more interesting on big endian > architectures where 'vfprintf' would be looking in the middle of an > int64 type. > > print_u/int now stick with native int size. > > Signed-off-by: Kevin Darbyshire-Bryant > --- > include/json_print.h | 2 +- > lib/json_print.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/json_print.h b/include/json_print.h > index 2ca7830a..45bc653d 100644 > --- a/include/json_print.h > +++ b/include/json_print.h > @@ -56,10 +56,10 @@ void close_json_array(enum output_type type, const char *delim); > print_color_##type_name(t, COLOR_NONE, key, fmt, value); \ > } > _PRINT_FUNC(int, int); > +_PRINT_FUNC(uint, unsigned int); > _PRINT_FUNC(bool, bool); > _PRINT_FUNC(null, const char*); > _PRINT_FUNC(string, const char*); > -_PRINT_FUNC(uint, uint64_t); > _PRINT_FUNC(hu, unsigned short); > _PRINT_FUNC(hex, unsigned int); > _PRINT_FUNC(0xhex, unsigned int); > diff --git a/lib/json_print.c b/lib/json_print.c > index 6518ba98..8d54d1d4 100644 > --- a/lib/json_print.c > +++ b/lib/json_print.c > @@ -117,8 +117,8 @@ void close_json_array(enum output_type type, const char *str) > } \ > } > _PRINT_FUNC(int, int); > +_PRINT_FUNC(uint, unsigned int); > _PRINT_FUNC(hu, unsigned short); > -_PRINT_FUNC(uint, uint64_t); > _PRINT_FUNC(lluint, unsigned long long int); > _PRINT_FUNC(float, double); > #undef _PRINT_FUNC I am concerned that this will break output of 64 bit statistics on 32 bit hosts.