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Re: A patch for ia32 hardware watchpoint.

> This is a patch for

I have problems with this patch.  See below.

> I only did it for Linux since it is not a perfect solution.

No, you also changed nm-go32.h, which is not related to Linux (AFAIK),
and changed the global definition of two macros on breakpoint.c.

> +		    val = target_insert_watchpoint (b->number, addr,
> +		    				    len, type);
> +#else

Please explain why is this needed.  The DJGPP version works well
without knowing the breakpoint number, but if there's a good reason
for passing b->number, it should be done on all x86 platforms.  So
let's discuss this.

> +		/* Don't return an error if we fail to insert
> +		   a hardware watchpoint due to the limited number
> +		   of hardware watchpoints availabel.  */
> +		val = (errno == EBUSY) ? 0 : -1;
> +	      }

Why is this a good idea?  The result of this is that GDB will not know
that it cannot insert a watchpoint until it actually resumes the
debuggee, which is too late in many cases; and the user gets confusing
error messages.  x86 doesn't have a good way of checking whether the
debug registers are enough to cover the requests, but whenever it
does, why not use it?

> @@ -5500,13 +5513,13 @@ watch_command_1 (arg, accessflag, from_t
>     in hardware return zero.  */
>  #endif
>  #endif

These are IMHO wrong: the number of debug registers required for a
particular region is a function of the address, not only size (e.g., a
single x86 debug register cannot watch a 32-bit region that isn't
aligned on 4-byte boundary).  If Linux, for some reason, doesn't need
the address (although I cannot see how could this be right, at least
for native debugging), please define a platform-specific macro instead
of overwriting system-wide defaults.

The DJGPP version actually *uses* the ADDR part of the above
definition, since it knows how to cover a region with several

> --- config/i386/nm-go32.h	2000/03/07 18:42:21
> +++ config/i386/nm-go32.h	2000/03/07 18:53:48
> @@ -44,10 +44,10 @@
>  #define TARGET_CAN_USE_HARDWARE_WATCHPOINT(type, cnt, ot) 1
>  /* Returns non-zero if we can use hardware watchpoints to watch a region
> -   whose address is ADDR and whose length is LEN.  */
> +   which represents VAL.  */
> -	go32_region_ok_for_watchpoint(addr,len)
> +	go32_region_ok_for_watchpoint((VALUE_ADDRESS (val) + VALUE_OFFSET (val)),TYPE_LENGTH (VALUE_TYPE (val)))

Please do not commit this one, it disables a valuable feature in the
DJGPP version.

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