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Re: va_list implementation on mips64 , with 32bit cross compiled

To: "wilbur.chan" <wilbur512@gmail.com>
Subject: Re: va_list implementation on mips64 , with 32bit cross compiled
From: David Daney <ddaney@caviumnetworks.com>
Date: Wed, 13 Oct 2010 17:15:00 -0700
Cc: Linux MIPS Mailing List <linux-mips@linux-mips.org>
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On 10/13/2010 05:06 PM, wilbur.chan wrote:
I am planning  to use va_list on a single module, however the
following code did not work properly.

typedef char *  va_list;
#define _INTSIZEOF(n)   ( (sizeof(n) + sizeof(int) - 1)&  ~(sizeof(int) - 1) )
#define va_start(ap,v)  ( ap = (va_list)&v + _INTSIZEOF(v) )
#define va_arg(ap,t)    ( *(t *)((ap += _INTSIZEOF(t)) - _INTSIZEOF(t)) )
#define va_end(ap)      ( ap = (va_list)0 )


You cannot arbitrarily define those macros with garbage and expect anything to work.

Replace all the above code with #include <stdarg.h>

Then do: man stdarg

That documents how it works.

David Daney


void test_val_list()
{
unsigned long test=0x1234;
test_printk("test:0x%x OK\n",aaa);
}

void test_printk(const char *format, ...)
{
va_list args;
va_start(args, format);
unsigned int v1 = va_arg(args,unsigned long);
printk("v1 is 0x%x\n",v1);
unsigned int v2 = va_arg(args,unsigned long);
printk("v2 is 0x%x\n",v2);
}


The result is :

v1 is 0x00000013

v2 is 0x00000019

Why this happened ? shouldn't v1 be 0x1234 here?

Thank you




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