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Re: [PATCH] PR gas/19896: Don't change defined symbol to undefined

On Fri, Apr 01, 2016 at 08:52:39AM -0700, H.J. Lu wrote:
> +.*: Assembler messages:
> +.*:6: Error: symbol `mempcpy' is already defined
> +.*:6: Error: can't change defined symbol `mempcpy' to undefined

This is a confusing error message.  Where in the user input is mempcpy
being made undefined?

> diff --git a/gas/testsuite/gas/elf/pr19896.s b/gas/testsuite/gas/elf/pr19896.s
> new file mode 100644
> index 0000000..92fbe11
> --- /dev/null
> +++ b/gas/testsuite/gas/elf/pr19896.s
> @@ -0,0 +1,6 @@
> +	.globl mempcpy
> +	.type mempcpy,%function
> +mempcpy:
> +	.byte 0
> +	.size mempcpy,.-mempcpy
> +	mempcpy = __mempcpy

Also, this testcase doesn't segfault on an old assembler like the
original in your bugzilla.  It seems you need an instruction like
"jmp" that sets up a new frag, or something like ".org 8" instead of
.byte.  Please commit with the ".org 8" change.

I think what we want instead in read.c:assign_symbol is the following.
It's a little different from the usual ignore_rest_of_line() after an
error because we don't want to skip over EOL in this function.  That
happens in the caller of assign_symbol (or caller's caller).  I'll
commit this after testing.

	PR 19896
	* read.c (assign_symbol): Consume rest of line after an error
	rather than continuing to process the line.

diff --git a/gas/read.c b/gas/read.c
index 35d44c1..a940ff3 100644
--- a/gas/read.c
+++ b/gas/read.c
@@ -3255,7 +3255,9 @@ assign_symbol (char *name, int mode)
 	  && !S_CAN_BE_REDEFINED (symbolP))
 	  as_bad (_("symbol `%s' is already defined"), name);
-	  symbolP = symbol_clone (symbolP, 0);
+	  ignore_rest_of_line ();
+	  input_line_pointer--;
+	  return;
       /* If the symbol is volatile, copy the symbol and replace the
 	 original with the copy, so that previous uses of the symbol will

Alan Modra
Australia Development Lab, IBM

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