Re: [RFA]: Fix for do_mixed_source_and_assembly in disasm.c

[Jason Molenda <jmolenda@apple.com>]

[-- Attachment #1: Type: text/plain, Size: 2136 bytes --]

Hi Jeff,

On Dec 17, 2003, at 1:15 PM, Jeff Johnston wrote:

> There are a few bugs in do_mixed_source_and_assembly() when dealing 
> with the ia64.

I hit one of the two bugs you're fixing last week, namely the double 
call to close off the list/tuple.  My first fix looked like yours, but 
I think a slight reworking of the loop is very desirable here.  Right 
now this loop looks approximately like this:


    Set close_list to 1 (the list/tuple will be closed at the end of 
this loop)

    First entry of a new source line number:
      Start a "src_and_asm_line" tuple, print the source line.
      Start a "line_asm_insn" list where instructions will be emitted.
      If we're not at the end of the mle array, and the next mle entry's 
source line number is not greater than the current source line entry, 
DON'T close off the list (close_list = 0)

    Print the assembly instructions for the current address range.

    If close_list is 1, close the tuple/list.


Which is a very convoluted way of writing a loop, and more importantly, 
this only works correctly for one or two assembly ranges for a single 
source line.  If you have a third, on the 2nd iter the tuple/list are 
closed and then on the 3rd you close them again.

Instead, this is more clear:


   First entry of a new source line number:
      Start a "src_and_asm_line" tuple, print the source line.
      Start a "line_asm_insn" list where instructions will be emitted.

   Print the assembly instructions for the current address range.

   If we're at the end of the mle array or the next entry in the array 
is a new source line, close off the list and tuple.


I also took the opportunity to combine two conditional statements - I 
won't push hard for that part of the change, but the rest is a clear 
improvement IMHO.

We only had this code path executed when we were using a compiler with 
a bug in it internally, so it's not too easy for me to reproduce/test 
this.  I've tried to combine my patch and yours against the current FSF 
TOT.  What do you think of my suggested additional change?  Can you try 
it on the IA64 test case you have?


Jason


[-- Attachment #2: pa.txt --]
[-- Type: text/plain, Size: 1992 bytes --]

Index: disasm.c
===================================================================
RCS file: /cvs/src/src/gdb/disasm.c,v
retrieving revision 1.17
diff -u -p -r1.17 disasm.c
--- disasm.c	24 Oct 2003 17:37:03 -0000	1.17
+++ disasm.c	18 Dec 2003 22:05:20 -0000
@@ -164,6 +164,8 @@ do_mixed_source_and_assembly (struct ui_
   CORE_ADDR pc;
   int num_displayed = 0;
   struct cleanup *ui_out_chain;
+  struct cleanup *ui_out_tuple_chain = NULL;
+  struct cleanup *ui_out_list_chain = NULL;
 
   mle = (struct dis_line_entry *) alloca (nlines
 					  * sizeof (struct dis_line_entry));
@@ -221,10 +223,6 @@ do_mixed_source_and_assembly (struct ui_
 
   for (i = 0; i < newlines; i++)
     {
-      struct cleanup *ui_out_tuple_chain = NULL;
-      struct cleanup *ui_out_list_chain = NULL;
-      int close_list = 1;
-      
       /* Print out everything from next_line to the current line.  */
       if (mle[i].line >= next_line)
 	{
@@ -275,22 +273,22 @@ do_mixed_source_and_assembly (struct ui_
 	  next_line = mle[i].line + 1;
 	  ui_out_list_chain
 	    = make_cleanup_ui_out_list_begin_end (uiout, "line_asm_insn");
-	  /* Don't close the list if the lines are not in order. */
-	  if (i < (newlines - 1) && mle[i + 1].line <= mle[i].line)
-	    close_list = 0;
 	}
 
       num_displayed += dump_insns (uiout, di, mle[i].start_pc, mle[i].end_pc,
 				   how_many, stb);
-      if (close_list)
+
+      /* When we've reached the end of the mle array, or we've seen the last
+         assembly range for this source line, close out the list/tuple.  */
+      if (i == (newlines - 1) || mle[i + 1].line > mle[i].line)
 	{
 	  do_cleanups (ui_out_list_chain);
 	  do_cleanups (ui_out_tuple_chain);
+          ui_out_tuple_chain = NULL;
+          ui_out_list_chain = NULL;
 	  ui_out_text (uiout, "\n");
-	  close_list = 0;
 	}
-      if (how_many >= 0)
-	if (num_displayed >= how_many)
+      if (how_many >= 0 && num_displayed >= how_many)
 	  break;
     }
   do_cleanups (ui_out_chain);