Date: Thu, 27 Jun 2013 13:52:01 +1000 From: Matthew Fernandez <matthew.fernandez@...ta.com.au> To: <musl@...ts.openwall.com> Subject: Use of size_t and ssize_t in mseek Hi all, My question refers to the latest git commit at time of writing, b17c75a4d539d7ec5b81cc7ce7ce6b065a87e7a6. My issue was encountered on ARM, but it applies to most 32-bit platforms. The function mseek() accesses a size_t variable, c->size, and casts this to a ssize_t. I know there aren't strong standards on what to expect from ssize_t, but the Musl C constants SIZE_MAX (== UINT32_MAX) and SSIZE_MAX (== LONG_MAX) seem to imply that you would be wise to assume ssize_t is signed and the same width as size_t. As a result, the cast I mentioned produces some unexpected results when operating on a file of size greater than SSIZE_MAX. In my case I had an in-memory file of size SIZE_MAX and was surprised to find I couldn't fseek this file. Is the code in mseek() correct? If so, I would recommend failing fmemopen() when the requested size is greater than SSIZE_MAX. OTOH perhaps I'm misunderstanding something more subtle here. If so, please correct me. Thanks, Matthew [It is perhaps worth noting that, yes, a UINT32_MAX-sized in-memory file on a 32-bit platform is a bit odd. In my case I don't know how big the file is until I've read its header. You could object that this is unwise, but either way I believe fmemopen/mseek should handle this case.] ________________________________ The information in this e-mail may be confidential and subject to legal professional privilege and/or copyright. National ICT Australia Limited accepts no liability for any damage caused by this email or its attachments.
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