Re: [lwip-devel] [bug #35587] Uninitialized pointer (David Brown)

[Eliot Blennerhassett]

> Note that despite this being part of the C standards, there are a few 
> compiler toolchains that stubbornly refuse to implement it.  TI's Code 
> Composer is one of these - it does not zero the statically allocated 
> uninitialised data at startup (unless you add your own code to do so). 
> It even has a comment in the manual, telling you that this behaviour is 
> non-standard!

Yes, this is a PITA!

We have ported lwip to TI tools and DSP/BIOSv5
(NO_SYS=0, not currently using TCP.
Used in these
http://www.audioscience.com/internet/products/cobranet/cobranet_if.htm )

Our solution is to get the linker to zero .bss and .far
SECTIONS {
        .bss {} > IRAM, fill = 0
        .far {} > SDRAM, fill = 0
        .far_notzeroed {} > SDRAM
        ...
}

We also patch lwip to place heap and mem pool in separate uninitialised
section, to limit the generated static image size:

+#pragma DATA_SECTION(memp_memory,".far_notzeroed");
 static u8_t memp_memory[MEM_ALIGNMENT - 1

+#pragma DATA_SECTION(ram_heap,".far_notzeroed");
 u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT];

BTW We are happy to share the DSP/BIOS port if there is any interest.

regards

Eliot Blennerhassett
AudioScience Inc.