[webkit-dev] malloc(0)

Adam Barth abarth at webkit.org
Tue Jun 12 15:08:48 PDT 2012

There was some discussion about how to handle malloc(0) a year or so
ago.  I don't remember if it was on webkit-dev, but you might want to
check the archives.  Eric Seidel might remember what conclusions (if
any) we came to.


On Tue, Jun 12, 2012 at 3:03 PM, Myles C. Maxfield
<myles.maxfield at gmail.com> wrote:
> Hello,
> I'm compiling WebKit with a malloc() implementation that returns NULL
> for malloc(0). According to C99, this is valid: "If the size of the
> space requested is zero, the behavior is implementation- defined:
> either a null pointer is returned, or the behavior is as if the size
> were some nonzero value, except that the returned pointer shall not be
> used to access an object."
> I noticed that this caused a problem in one particular place
> (WTF::StringImpl::getData16SlowCase()) where the code allocates
> (constant * length) bytes for an (empty) string, and provides an
> accessor that exposes this pointer. This pointer was being passed to
> ICU, which didn't perform the requested function because it looked
> like one of the arguments was invalid, even though it was just empty.
> I have worked around this one particular occurrence in my local
> version of WebKit fork, but I'm wondering how often this pattern
> occurs. Is my fix worth upstreaming?  Is it worth trying to find,
> "fix," and upstream every occurrence of this pattern? Or is this
> particular behavior of malloc() an unstated requirement of building
> WebKit? If the latter is true, perhaps it's worth explicitly stating
> this somewhere? What is the opinion of the community?
> Thanks,
> Myles
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