[lwip-devel] Issue with gcc 6.3 s390x with 32 bit - format error ?

[Ivan Warren]

Hello all,

I am getting the following error on git head while cross compiling 
lwipcore (x64->s390x) on debian :

/home/ivan/lwip/src/lwip/src/core/mem.c:1005:54: error: format ‘%u’ 
expects argument of type ‘unsigned int’, but argument 2 has type ‘size_t 
{aka long unsigned int}’ [-Werror=format=]
     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("mem_calloc: 
could not allocate %"SZT_F" bytes\n", alloc_size));

This is very odd since I am compiling this (through a wrapper) with gcc 
-m31 (read -m32 .. the 31 is a s390/s390x quirk) and "unsigned int" have 
exactly the same width and sign as "long unsigned int" (32 bit unsigned 
value) - so should NOT trigger the gcc warning ! (gcc bug ?)

To me there is no error in lwip at this point (SZT_F is defined in 
arch.h as PRIuPTR which should work just fine).

A s390x 64 bit compiles just fine (but doesn't fit in my project)

Changing SZT_F to "lu" (or defining LWIP_HAVE_INTTYPES as 0 and 
providing my own definition of SZT_F) solves my problem (as a workaround 
only.. this is definitelly not a permament solution).

Just food for thought/thinking out loud.. (not a pressing issue since I 
have an easy workaround)

--Ivan

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