Date: Tue, 29 Jun 2010 08:21:17 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Jaakko Heinonen <jh@freebsd.org> Cc: freebsd-bugs@freebsd.org Subject: Re: kern/144307: ENOENT set unnecessarily under certain circumstances when malloc is called / fails Message-ID: <20100629081501.K2710@besplex.bde.org> In-Reply-To: <201006282020.o5SKK3OG063671@freefall.freebsd.org> References: <201006282020.o5SKK3OG063671@freefall.freebsd.org>
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On Mon, 28 Jun 2010, Jaakko Heinonen wrote: > On 2010-06-28, Garrett Cooper wrote: > > Or the malloc(3) call could be fixed with the couple of lines I > > noted (well, adlibbed of course... > > > > Which I agree with, but shouldn't we fix malloc(3) (and any other > > function calls that depend on malloc(3) for sensible results)? > > It's not required for POSIX compliance at least. Did you actually read > the quotes from POSIX? > > "The value of errno should only be examined when it is indicated to be > valid by a function's return value." > > "The setting of errno after a successful call to a function is > unspecified unless the description of that function specifies that errno > shall not be modified." > > In other words the value of errno is undefined and shouldn't be unspecified > examined unless malloc(3) returns NULL. Not quite even then. malloc(0) may return NULL, so errno shouldn't be examined unless malloc() returns NULL and its arg (when converted to a size_t) is nonzero. Maybe more of these bugs could be found by setting errno to EDOOFUS in malloc() and other commonly used library functions :-). This is easier to recognize than say ENOTTY from isatty() in stream initialization on non-ttys. Bruce
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