Re: gcj/383: duplicate switch label problems

[Tom Tromey <tromey at redhat dot com>]

The following reply was made to PR gcj/383; it has been noted by GNATS.

From: Tom Tromey <tromey@redhat.com>
To: apbianco@cygnus.com
Cc: Bryce McKinlay <bryce@albatross.co.nz>, java-gnats@sourceware.cygnus.com
Subject: Re: gcj/383: duplicate switch label problems
Date: 12 Dec 2000 13:48:38 -0700

 Alex> I thought so too. But then I can't remember to which extend
 Alex> gcc's middle end is responsible for the detection of multiple
 Alex> entries.
 
 I looked at this bug this morning.
 
 java_lang_expand_expr() does the checking for duplicate case labels.
 However, this is not called when -C is given.  I guess that isn't too
 suprising.
 
 If you look at jcf-write.c:generate_bytecode_insns() you will see a
 FIXME comment indicating that the code should check for duplicates.
 
 I wrote a simple patch to do the checking (appended).  However, this
 patch has a couple of problems:
 
 1. It doesn't print the correct line number for the duplicate label
 2. Even when an error is generated gcj will generate a .class file
 
 
 I don't see how to do error reporting from jcf-write.  Maybe the only
 fix is to check for duplicate labels (and any other kind of
 source-level error) before handing the tree to the .class generator.
 
 This is more work since it involves tracking down the right place to
 put the checking code.
 
 Tom
 
 2000-12-12  Tom Tromey  <tromey@redhat.com>
 
 	* jcf-write.c (generate_bytecode_insns): Check for duplicate case
 	labels.
 
 Index: jcf-write.c
 ===================================================================
 RCS file: /cvs/gcc/egcs/gcc/java/jcf-write.c,v
 retrieving revision 1.70
 diff -u -r1.70 jcf-write.c
 --- jcf-write.c	2000/12/06 18:55:42	1.70
 +++ jcf-write.c	2000/12/12 20:32:37
 @@ -1726,6 +1726,7 @@
  	else
  	  {
  	    HOST_WIDE_INT i;
 +	    int found_error = 0;
  	    /* Copy the chain of relocs into a sorted array. */
  	    struct jcf_relocation **relocs = (struct jcf_relocation **)
  	      xmalloc (sw_state.num_cases * sizeof (struct jcf_relocation *));
 @@ -1737,6 +1738,22 @@
  	    for (reloc = sw_state.cases;  reloc != NULL;  reloc = reloc->next)
  	      {
  		HOST_WIDE_INT case_value = reloc->offset;
 +		struct jcf_relocation *r2;
 +
 +		/* Check for duplicates.  */
 +		for (r2 = sw_state.cases; r2 != reloc; r2 = r2->next)
 +		  {
 +		    HOST_WIDE_INT v2 = r2->offset;
 +		    if (case_value == v2 && reloc != r2)
 +		      {
 +			/* FIXME: we really should print the locations
 +			   of the duplicate and of the original.  */
 +			error ("Duplicate case label: `%d'",
 +			       (int) case_value);
 +			found_error = 1;
 +		      }
 +		  }
 +
  		while (gap_end < sw_state.num_cases)
  		  {
  		    struct jcf_relocation *end = relocs[gap_end];
 @@ -1757,8 +1774,12 @@
  		/* Note we don't check for duplicates.  FIXME! */
  	      }
  
 -	    if (2 * sw_state.num_cases
 -		>= sw_state.max_case - sw_state.min_case)
 +	    if (found_error)
 +	      {
 +		/* Nothing.  */
 +	      }
 +	    else if (2 * sw_state.num_cases
 +		     >= sw_state.max_case - sw_state.min_case)
  	      { /* Use tableswitch. */
  		int index = 0;
  		RESERVE (13 + 4 * (sw_state.max_case - sw_state.min_case + 1));