# [PATCH 2/2] obstack.c: Fix some sparse warnings 3 messages from 2011-09-11 to 2011-09-13. Participants: Ramsay Jones, Sverre Rabbelier. Thread: https://gitlist.dev/t/28362 ## Ramsay Jones, 2011-09-11 19:26 Subject: [PATCH 2/2] obstack.c: Fix some sparse warnings Message-ID: <4E6D0B7D.9070602@ramsay1.demon.co.uk> URL: https://gitlist.dev/e/4E6D0B7D.9070602%40ramsay1.demon.co.uk ``` In particular, sparse issues the following warnings: compat/obstack.c:176:17: warning: Using plain integer as NULL pointer compat/obstack.c:224:17: warning: Using plain integer as NULL pointer compat/obstack.c:324:16: warning: Using plain integer as NULL pointer compat/obstack.c:329:16: warning: Using plain integer as NULL pointer compat/obstack.c:347:16: warning: Using plain integer as NULL pointer compat/obstack.c:362:19: warning: Using plain integer as NULL pointer compat/obstack.c:379:29: warning: Using plain integer as NULL pointer compat/obstack.c:399:1: error: symbol 'print_and_abort' redeclared with \ different type (originally declared at compat/obstack.c:95) \ - different modifiers Signed-off-by: Ramsay Jones --- compat/obstack.c | 15 +++++++-------- 1 files changed, 7 insertions(+), 8 deletions(-) diff --git a/compat/obstack.c b/compat/obstack.c index a89ab5b..e276ccd 100644 --- a/compat/obstack.c +++ b/compat/obstack.c @@ -173,7 +173,7 @@ _obstack_begin (struct obstack *h, alignment - 1); h->chunk_limit = chunk->limit = (char *) chunk + h->chunk_size; - chunk->prev = 0; + chunk->prev = NULL; /* The initial chunk now contains no empty object. */ h->maybe_empty_object = 0; h->alloc_failed = 0; @@ -221,7 +221,7 @@ _obstack_begin_1 (struct obstack *h, int size, int alignment, alignment - 1); h->chunk_limit = chunk->limit = (char *) chunk + h->chunk_size; - chunk->prev = 0; + chunk->prev = NULL; /* The initial chunk now contains no empty object. */ h->maybe_empty_object = 0; h->alloc_failed = 0; @@ -321,12 +321,12 @@ _obstack_allocated_p (struct obstack *h, void *obj) /* We use >= rather than > since the object cannot be exactly at the beginning of the chunk but might be an empty object exactly at the end of an adjacent chunk. */ - while (lp != 0 && ((void *) lp >= obj || (void *) (lp)->limit < obj)) + while (lp != NULL && ((void *) lp >= obj || (void *) (lp)->limit < obj)) { plp = lp->prev; lp = plp; } - return lp != 0; + return lp != NULL; } /* Free objects in obstack H, including OBJ and everything allocate @@ -344,7 +344,7 @@ obstack_free (struct obstack *h, void *obj) /* We use >= because there cannot be an object at the beginning of a chunk. But there can be an empty object at that address at the end of another chunk. */ - while (lp != 0 && ((void *) lp >= obj || (void *) (lp)->limit < obj)) + while (lp != NULL && ((void *) lp >= obj || (void *) (lp)->limit < obj)) { plp = lp->prev; CALL_FREEFUN (h, lp); @@ -359,7 +359,7 @@ obstack_free (struct obstack *h, void *obj) h->chunk_limit = lp->limit; h->chunk = lp; } - else if (obj != 0) + else if (obj != NULL) /* obj is not in any of the chunks! */ abort (); } @@ -376,7 +376,7 @@ _obstack_memory_used (struct obstack *h) register struct _obstack_chunk* lp; register int nbytes = 0; - for (lp = h->chunk; lp != 0; lp = lp->prev) + for (lp = h->chunk; lp != NULL; lp = lp->prev) { nbytes += lp->limit - (char *) lp; } @@ -395,7 +395,6 @@ _obstack_memory_used (struct obstack *h) # endif static void -__attribute__ ((noreturn)) print_and_abort (void) { /* Don't change any of these strings. Yes, it would be possible to add -- 1.7.6 ``` ## Sverre Rabbelier, 2011-09-11 21:56 Subject: Re: [PATCH 2/2] obstack.c: Fix some sparse warnings Message-ID: URL: https://gitlist.dev/e/CAGdFq_ifU2WWbCpRY_EFY%3D_hwwtFs0eqMhJ7sRoUhrivABFoFw%40mail.gmail.com In-Reply-To: <4E6D0B7D.9070602@ramsay1.demon.co.uk> ``` Heya, On Sun, Sep 11, 2011 at 21:26, Ramsay Jones wrote: >    compat/obstack.c:399:1: error: symbol 'print_and_abort' redeclared with \ >        different type (originally declared at compat/obstack.c:95) \ >        - different modifiers > @@ -395,7 +395,6 @@ _obstack_memory_used (struct obstack *h) >  # endif > >  static void > -__attribute__ ((noreturn)) >  print_and_abort (void) >  { >   /* Don't change any of these strings.  Yes, it would be possible to add Wouldn't the better solution be to add noreturn to the declaration at compat/obstack.c:95? -- Cheers, Sverre Rabbelier ``` ## Ramsay Jones, 2011-09-13 23:18 Subject: Re: [PATCH 2/2] obstack.c: Fix some sparse warnings Message-ID: <4E6FE4DF.7060200@ramsay1.demon.co.uk> URL: https://gitlist.dev/e/4E6FE4DF.7060200%40ramsay1.demon.co.uk In-Reply-To: ``` Sverre Rabbelier wrote: > Heya, > > On Sun, Sep 11, 2011 at 21:26, Ramsay Jones wrote: >> compat/obstack.c:399:1: error: symbol 'print_and_abort' redeclared with \ >> different type (originally declared at compat/obstack.c:95) \ >> - different modifiers > >> @@ -395,7 +395,6 @@ _obstack_memory_used (struct obstack *h) >> # endif >> >> static void >> -__attribute__ ((noreturn)) >> print_and_abort (void) >> { >> /* Don't change any of these strings. Yes, it would be possible to add > > Wouldn't the better solution be to add noreturn to the declaration at > compat/obstack.c:95? Hmm, well ... maybe; it is at least debatable. But I decided no! :-D First, although I would not dismiss the possibility of some optimization of the code of print_and_abort() (the *callee*), the main benefit of the noreturn attribute should in fact be at the call sites (ie the *caller*). So, yes, in general, the declaration of the function should have the noreturn attribute applied, in addition to the definition, in order to allow the compiler to apply some optimizations to the call sites. [Note, also, that we should use the NORETURN and NORETURN_PTR macros.] In this case, however, there are no (direct) call sites. This function would only be called indirectly via the 'obstack_alloc_failed_handler' function pointer. So, this would require the use of NORETURN_PTR on that function pointer. In order to keep both the compiler(s) and sparse happy, the required change would look like the diff given at the end of this mail. This would work fine, and I would happily change the patch to include this if it is deemed the better approach. However, I looked at the call sites in _obstack_begin[_1](), and _obstack_newchunck() and could not see any great opportunity for optimizing the code ... so I decided to go for the simpler patch ... ATB, Ramsay Jones -- >8 -- diff --git a/compat/obstack.c b/compat/obstack.c index a89ab5b..2029b8f 100644 --- a/compat/obstack.c +++ b/compat/obstack.c @@ -92,8 +92,8 @@ enum abort gracefully or use longjump - but shouldn't return. This variable by default points to the internal function `print_and_abort'. */ -static void print_and_abort (void); -void (*obstack_alloc_failed_handler) (void) = print_and_abort; +static void NORETURN print_and_abort (void); +NORETURN_PTR void (*obstack_alloc_failed_handler) (void) = print_and_abort; # ifdef _LIBC # if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_3_4) @@ -395,7 +395,7 @@ _obstack_memory_used (struct obstack *h) # endif static void -__attribute__ ((noreturn)) +NORETURN print_and_abort (void) { /* Don't change any of these strings. Yes, it would be possible to add diff --git a/compat/obstack.h b/compat/obstack.h index d178bd6..122f93f 100644 --- a/compat/obstack.h +++ b/compat/obstack.h @@ -194,7 +194,7 @@ void obstack_free (struct obstack *, void *); more memory. This can be set to a user defined function which should either abort gracefully or use longjump - but shouldn't return. The default action is to print a message and abort. */ -extern void (*obstack_alloc_failed_handler) (void); +extern NORETURN_PTR void (*obstack_alloc_failed_handler) (void); /* Pointer to beginning of object being allocated or to be allocated next. Note that this might not be the final address of the object ```