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Re: Re: [lwip-devel] possible mistake in mem.h

From: Iordan Neshev
Subject: Re: Re: [lwip-devel] possible mistake in mem.h
Date: Wed, 30 Jan 2008 19:52:24 +0100
User-agent: Thunderbird (Windows/20070509)

Goldschmidt Simon wrote:
>> Please look at mem.h, line 83:
>>  void *mem_calloc(size_t count, size_t size);
>> We think that the type should be mem_size_t, not just size_t;
>> Under VisualC there is no problem because size_t is defined.
>> However, when we ported the source to the embedded target, its
> compiler complained.
>> typedef  u16_t size_t; solves the problem, but it's not the right way
> to do it.
>> Are we right?
> As far as I know, the type 'size_t' is C-standard. If it is not defined
> on your platform, you will have problems with the socket layer also. If
> it is not defined, defining it in your port's 'cc.h' will be the right
> thing to do.

It is C standard, but only if you have #included <stddef.h>. Perhaps that's
what mem.h should do if it is referencing size_t.
I agree that <stddef.h> should be included. But I still think it should be mem_size_t. Read carefully: There is a stripped copy/paste from the source of mem.h: #if MEM_SIZE > 64000l typedef u32_t mem_size_t; #define MEM_SIZE_F U32_F #else typedef u16_t mem_size_t; #define MEM_SIZE_F U16_F #endif /* MEM_SIZE > 64000 */ .... #if MEM_LIBC_MALLOC /* aliases for C library malloc() */ ... #else /* MEM_LIBC_MALLOC */ ... void *mem_malloc(mem_size_t size); void *mem_calloc(size_t count, size_t size); // mem_size_t??? ... #endif /* MEM_LIBC_MALLOC */ This is from mem.c, line 564: void *mem_calloc(size_t count, size_t size) { void *p; p = mem_malloc(count * size); if (p) { memset(p, 0, count * size); } return p; } mem_size_t is 16 or 32-bit long, depending on the system memory available. Notice that mem_calloc() takes size_t argument and passes it to mem_malloc() which, however, takes mem_size_t; While size_t and mem_size_t happen to be both of the same length, everything is OK. Guess what happens when size_t is 32-bit, and mem_size_t is 16-t long. I noticed some more "mistakes" like this one, but I'll post them separately if you don't mind. Regards Iordan Neshev Daisy Technology

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