# [PATCH] Fix some sparse warnings 5 messages from 2013-07-18 to 2013-07-21. Participants: Ramsay Jones, Jeff King, Jonathan Nieder, Junio C Hamano. Thread: https://gitlist.dev/t/34477 ## Ramsay Jones, 2013-07-18 20:25 Subject: [PATCH] Fix some sparse warnings Message-ID: <51E84F4E.3050600@ramsay1.demon.co.uk> URL: https://gitlist.dev/e/51E84F4E.3050600%40ramsay1.demon.co.uk ``` Sparse issues some "Using plain integer as NULL pointer" warnings. Each warning relates to the use of an '{0}' initialiser expression in the declaration of an 'struct object_info'. The first field of this structure has pointer type. Thus, in order to suppress these warnings, we replace the initialiser expression with '{NULL}'. Signed-off-by: Ramsay Jones --- This was built on the next branch. ATB, Ramsay Jones sha1_file.c | 2 +- streaming.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/sha1_file.c b/sha1_file.c index 4c2365f..e4ab0a4 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -2440,7 +2440,7 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi) int sha1_object_info(const unsigned char *sha1, unsigned long *sizep) { - struct object_info oi = {0}; + struct object_info oi = {NULL}; oi.sizep = sizep; return sha1_object_info_extended(sha1, &oi); diff --git a/streaming.c b/streaming.c index cac282f..5710065 100644 --- a/streaming.c +++ b/streaming.c @@ -135,7 +135,7 @@ struct git_istream *open_istream(const unsigned char *sha1, struct stream_filter *filter) { struct git_istream *st; - struct object_info oi = {0}; + struct object_info oi = {NULL}; const unsigned char *real = lookup_replace_object(sha1); enum input_source src = istream_source(real, type, &oi); -- 1.8.3 ``` ## Jeff King, 2013-07-18 20:36 Subject: Re: [PATCH] Fix some sparse warnings Message-ID: <20130718203640.GB15735@sigill.intra.peff.net> URL: https://gitlist.dev/e/20130718203640.GB15735%40sigill.intra.peff.net In-Reply-To: <51E84F4E.3050600@ramsay1.demon.co.uk> ``` On Thu, Jul 18, 2013 at 09:25:50PM +0100, Ramsay Jones wrote: > Sparse issues some "Using plain integer as NULL pointer" warnings. > Each warning relates to the use of an '{0}' initialiser expression > in the declaration of an 'struct object_info'. The first field of > this structure has pointer type. Thus, in order to suppress these > warnings, we replace the initialiser expression with '{NULL}'. > > Signed-off-by: Ramsay Jones Acked-by: Jeff King I thought at first we would need one more for the new callsite I added in my series, but we use memset() in that instance, so it is fine. -Peff ``` ## Ramsay Jones, 2013-07-20 19:26 Subject: Re: [PATCH] Fix some sparse warnings Message-ID: <51EAE463.4010705@ramsay1.demon.co.uk> URL: https://gitlist.dev/e/51EAE463.4010705%40ramsay1.demon.co.uk In-Reply-To: <20130718203640.GB15735@sigill.intra.peff.net> ``` Jeff King wrote: > On Thu, Jul 18, 2013 at 09:25:50PM +0100, Ramsay Jones wrote: > >> Sparse issues some "Using plain integer as NULL pointer" warnings. >> Each warning relates to the use of an '{0}' initialiser expression >> in the declaration of an 'struct object_info'. The first field of >> this structure has pointer type. Thus, in order to suppress these >> warnings, we replace the initialiser expression with '{NULL}'. >> >> Signed-off-by: Ramsay Jones > > Acked-by: Jeff King > > I thought at first we would need one more for the new callsite I added > in my series, but we use memset() in that instance, so it is fine. On an almost unrelated note ... I am now getting the following sparse warnings: pack-revindex.c:105:23: warning: memset with byte count of 262144 This is a little annoying, since there is no way to turn this off. :( (which I consider a bug in sparse). Sparse has special-case code to check calls to memset(), memcpy(), copy_to_user() and copy_from_user(). The code that checks the byte count argument looks like: static void check_byte_count(struct instruction *insn, pseudo_t count) { if (!count) return; if (count->type == PSEUDO_VAL) { long long val = count->value; if (val <= 0 || val > 100000) warning(insn->pos, "%s with byte count of %lld", show_ident(insn->func->sym->ident), val); return; } /* OK, we could try to do the range analysis here */ } I will just ignore this for now. ;-) ATB, Ramsay Jones ``` ## Jonathan Nieder, 2013-07-21 17:39 Subject: Re: [PATCH] Fix some sparse warnings Message-ID: <20130721173936.GA10647@elie.Belkin> URL: https://gitlist.dev/e/20130721173936.GA10647%40elie.Belkin In-Reply-To: <51E84F4E.3050600@ramsay1.demon.co.uk> ``` Hi, Ramsay Jones wrote: > Sparse issues some "Using plain integer as NULL pointer" warnings. > Each warning relates to the use of an '{0}' initialiser expression > in the declaration of an 'struct object_info'. The first field of > this structure has pointer type. Thus, in order to suppress these > warnings, we replace the initialiser expression with '{NULL}'. I agree that this is worth solving but the fix feels like a move in the wrong direction. Before this patch, the initialization says "= {0}", which basically means "memset it to 0". Afterward, the initializer depends on the order of fields in the struct. How about something like the following? diff --git i/cache.h w/cache.h index f2915509..ba028b75 100644 --- i/cache.h +++ w/cache.h @@ -1124,6 +1124,7 @@ struct object_info { } packed; } u; }; +#define OBJECT_INFO_INIT { NULL, NULL, OI_CACHED, { { NULL, 0, 0 } } } extern int sha1_object_info_extended(const unsigned char *, struct object_info *); /* Dumb servers support */ diff --git i/sha1_file.c w/sha1_file.c index 6baed676..2d812b8d 100644 --- i/sha1_file.c +++ w/sha1_file.c @@ -2421,7 +2421,7 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi) int sha1_object_info(const unsigned char *sha1, unsigned long *sizep) { - struct object_info oi = {0}; + struct object_info oi = OBJECT_INFO_INIT; oi.sizep = sizep; return sha1_object_info_extended(sha1, &oi); diff --git i/streaming.c w/streaming.c index cac282f0..b4c40ad9 100644 --- i/streaming.c +++ w/streaming.c @@ -135,7 +135,7 @@ struct git_istream *open_istream(const unsigned char *sha1, struct stream_filter *filter) { struct git_istream *st; - struct object_info oi = {0}; + struct object_info oi = OBJECT_INFO_INIT; const unsigned char *real = lookup_replace_object(sha1); enum input_source src = istream_source(real, type, &oi); ``` ## Junio C Hamano, 2013-07-21 20:58 Subject: Re: [PATCH] Fix some sparse warnings Message-ID: <7vmwpfsk8d.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7vmwpfsk8d.fsf%40alter.siamese.dyndns.org In-Reply-To: <20130721173936.GA10647@elie.Belkin> ``` Jonathan Nieder writes: > How about something like the following? > > diff --git i/cache.h w/cache.h > index f2915509..ba028b75 100644 > --- i/cache.h > +++ w/cache.h > @@ -1124,6 +1124,7 @@ struct object_info { > } packed; > } u; > }; > +#define OBJECT_INFO_INIT { NULL, NULL, OI_CACHED, { { NULL, 0, 0 } } } There are quite a many hits from $ git grep '= { *NULL *};' only some of which are "char *var[] = { NULL }", which is perfectly fine, but others are to initialise "struct foo" (or "foo_t" which is typedef'ed) that share the same "writing NULL means the initialiser knows the order of the fields". I doubt if the above #define is a maintainable solution, and worse yet, thinking about the fact that such a macro is necessary only for a structure whose first field happens to be of a pointer type, it strongly suggests me that it is not conceptually the right thing to do. Can't we have sparse fixed (or skip this specific warning) instead? ```