v850-elf-gcc, va_list
markku.pihlajamaa@luukku.com
markku.pihlajamaa@luukku.com
Thu Apr 18 02:38:00 GMT 2002
Hello everybody!
I suppose my first post was catched by the spam checking,
so I am trying another time.
I am doing some tests with the GNU C cross compiler,
configured for the v850-elf target. The compiler
is run on a PC and the operating system is
Red Hat Linux 7.1.
I have such a problem with the variable argument lists
that the first optional argument is not expanded by
va_arg() at all, but is skipped. In the example
below the out() function is called four times,
but the parameter gets bad values: 2, 3, 4 and a random
number instead of 1, 2, 3 and 4.
The C code, compiling command I have used and the
assembly output produced (with my comments added)
can be seen below.
Any ideas are welcomed.
Regards,
Markku
----------------------------------------------------
#include <stdarg.h>
extern int out ( int );
void test( int parc, ... )
{
va_list list;
va_start( list, parc );
while( parc )
{
int i;
i = va_arg( list, int );
out( i );
parc --;
}
va_end( list );
}
int main( void )
{
test( 4, 1, 2, 3, 4 );
return 0;
}
----------------------------------------------------
[markku@linux1 va_list]$ v850-elf-gcc -S -v test.c
Reading specs from /usr/local/lib/gcc-lib/v850-elf/2.96-xscale-
010827/specs
gcc version 2.96-xscale-010827
/usr/local/lib/gcc-lib/v850-elf/2.96-xscale-010827/cpp -lang-c -v -
D__GNUC__=2
-D__GNUC_MINOR__=96 -D__v851__ -D__v850 -D__v851__ -D__v850 -
D__v850__ test.c /t
mp/cc5YEVvf.i
GNU CPP version 2.96-xscale-010827 (cpplib)
(NEC V850)
ignoring nonexistent directory `/usr/local/v850-elf/sys-include'
#include "..." search starts here:
#include <...> search starts here:
/usr/local/lib/gcc-lib/v850-elf/2.96-xscale-010827/include
/usr/local/v850-elf/include
End of search list.
/usr/local/lib/gcc-lib/v850-elf/2.96-xscale-
010827/cc1 /tmp/cc5YEVvf.i -quiet -
dumpbase test.c -version -o test.s
GNU C version 2.96-xscale-010827 (v850-elf) compiled by GNU C version
2.96 20000
731 (Red Hat Linux 7.1 2.96-81).
[markku@linux1 va_list]$ cat test.s
.file "test.c"
gcc2_compiled.:
.section .text
.align 1
.global _test
.type _test,@function
_test:
st.w r6,0[sp]
st.w r7,4[sp]
st.w r8,8[sp]
st.w r9,12[sp]
----------------------------------------------------
The copies of the arguments are in the top of
stack at this point:
1st 0[sp]
2nd 4[sp]
3rd 8[sp]
4th 12[sp]
5th 16[sp] (pushed by the caller)
----------------------------------------------------
addi -36,sp,sp
st.w r31,32[sp]
st.w r28,28[sp]
st.w r29,24[sp]
mov sp,r29
----------------------------------------------------
r29 is used as a frame pointer
----------------------------------------------------
st.w r6,36[r29]
----------------------------------------------------
loop counter initialisation, actually done at _test:
----------------------------------------------------
addi 40,r29,r10
st.w r10,20[r29]
----------------------------------------------------
20[r29] points to the next argument, initially 40[r29]
or the copy of the 2nd argument
----------------------------------------------------
.L3:
ld.w 36[r29],r10
cmp r0,r10
bne .L5
br .L4
.L5:
ld.w 20[r29],r10
addi 4,r10,r11
st.w r11,20[r29]
----------------------------------------------------
the address of the next argument value has been read,
incremented and written back
----------------------------------------------------
ld.w 20[r29],r28
----------------------------------------------------
the address that has already been incremented
is read again; this way the first optional argument
is ignored
----------------------------------------------------
ld.w 0[r28],r10
st.w r10,16[r29]
ld.w 16[r29],r6
jarl _out,r31
ld.w 36[r29],r10
addi -1,r10,r11
st.w r11,36[r29]
br .L3
.L4:
.L2:
mov r29,sp
ld.w 32[sp],r31
ld.w 28[sp],r28
ld.w 24[sp],r29
addi 36,sp,sp
jmp [r31]
.Lfe1:
.size _test,.Lfe1-_test
.align 1
.global _main
.type _main,@function
_main:
addi -28,sp,sp
st.w r31,24[sp]
st.w r29,20[sp]
mov sp,r29
mov 4,r10
st.w r10,16[sp]
mov 4,r6
mov 1,r7
mov 2,r8
mov 3,r9
jarl _test,r31
mov 0,r10
br .L6
.L6:
mov r29,sp
ld.w 24[sp],r31
ld.w 20[sp],r29
addi 28,sp,sp
jmp [r31]
.Lfe2:
.size _main,.Lfe2-_main
.ident "GCC: (GNU) 2.96-xscale-010827"
----------------------------------------------------
...............................................
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