Re: extern variable

[sumanth <sumanth.gundapneni@redpinesignals.com>]

Hi Jim,
that seems to be a promising solution.
If I keep the prefix "_" for a global variable , there is a problem in 
accessing it in gdb...let me explain you with an example

Eg: file1.c
int a = 10;
int main()
{
int b =10;
int c;
c = add( a , b);
return 0;
}

file2.c

int add( int x, int y)
{
return x+y ;
}

 > mycompiler-gcc -g file1.c file2.c
 > mycompiler-gdb a.out
  >> when i print "a" in file1.c , i am able to see value 10;
  >> when i print "a" int file2.c, it prints , no symbol defined. 
Instead I can access it with " print _a"

Thats the problem; guess i am clear this time.

prefixing registers is out of scope for me , as people got used to 
register names r0, r1......

Regards,
Sumanth G

Jim Wilson wrote:
> On Mon, 2009-08-03 at 09:44 +0530, sumanth wrote:
>   
>>        How can i make sure my tool chain knows the difference between 
>> global variable r0 and register r0.
>>     
>
> The simple solution is to either add a prefix to variable names, or to
> add a prefix to register names.  In ELF, the convention is to not add a
> prefix to variables names, we add a prefix to register names instead if
> we need one, e.g. %eax on i386, or $4 on mips.
>
> You can of course choose to add a prefix to variable names.  It just
> isn't the convention.  See for instance how the arm-elf port works when
> you use the -fleading-underscore option.
>
> A less simple solution is to have an assembler syntax that avoids
> ambiguity between register names and variable names.  If for instance
> you have a move instruction that can accept either a register or a
> variable as source, then you have an ambiguity.  You could instead have
> a load instruction for reading memory, and a move instruction for
> reading registers, and then you don't have an ambiguity anymore.  You
> can also do things with addressing modes and relocation operators to
> reduce ambiguities.
>
> Jim
>
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