[PATCH 1/2] [PR symtab/17276]: Coalesce line number entries.

[Doug Evans <dje at google dot com>]

Hi.

This is the first of two patches to fix 17276.

The problem here is that clang can emit multiple line number entries
for the same line, e.g., for

  for (i = 0; i < 100000; i++); // line #34

clang will emit four line number entries:

The Directory Table:
  ../../../binutils-gdb/gdb/testsuite/gdb.base

 The File Name Table:
  Entry Dir     Time    Size    Name
  1     1       0       0       watchpoint-reuse-slot.c

 Line Number Statements:
  Extended opcode 2: set Address to 0x400600
  Advance Line by 29 to 30
  Copy
  Set column to 3
  Set prologue_end to true
  Special opcode 160: advance Address by 11 to 0x40060b and Line by 1 to 31
  Set column to 8
  Special opcode 106: advance Address by 7 to 0x400612 and Line by 3 to 34
  Extended opcode 4: set Discriminator to 4
  Special opcode 103: advance Address by 7 to 0x400619 and Line by 0 to 34
  Extended opcode 4: set Discriminator to 2
  Special opcode 201: advance Address by 14 to 0x400627 and Line by 0 to 34
  Set column to 27
  Extended opcode 4: set Discriminator to 3
  Special opcode 75: advance Address by 5 to 0x40062c and Line by 0 to 34
  Set column to 3
  Extended opcode 4: set Discriminator to 0
  Advance PC by constant 17 to 0x40063d
  Special opcode 63: advance Address by 4 to 0x400641 and Line by 2 to 36
  Advance PC by 2 to 0x400643
  Extended opcode 1: End of Sequence

This confuses gdb because a pc can be in the middle of the source line,
and yet at the start of a line number entry.

This patch is just cleanup, no functional changes.
It wraps some operations in functions to abstract away the details.

2014-08-15  Doug Evans  <dje@google.com>

	* buildsym.h (record_line_ftype): New typedef.
	(record_line): Use it.
	* dwarf2read.c (dwarf_record_line, dwarf_finish_line): New functions.
	(dwarf_decode_lines_1): Call them.

diff --git a/gdb/buildsym.h b/gdb/buildsym.h
index 57467c7..8ce01b2 100644
--- a/gdb/buildsym.h
+++ b/gdb/buildsym.h
@@ -171,6 +171,10 @@ EXTERN int context_stack_size;
 
 EXTERN int within_function;
 
+/* The type of the record_line function.  */
+typedef void (record_line_ftype) (struct subfile *subfile, int line,
+				  CORE_ADDR pc);
+
 
 
 #define next_symbol_text(objfile) (*next_symbol_text_func)(objfile)
@@ -236,7 +240,7 @@ extern struct context_stack *push_context (int desc, CORE_ADDR valu);
 
 extern struct context_stack *pop_context (void);
 
-extern void record_line (struct subfile *subfile, int line, CORE_ADDR pc);
+extern record_line_ftype record_line;
 
 extern void start_symtab (const char *name, const char *dirname,
 			  CORE_ADDR start_addr);
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 801f05d..2017821 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -17172,6 +17172,32 @@ noop_record_line (struct subfile *subfile, int line, CORE_ADDR pc)
   return;
 }
 
+/* Use P_RECORD_LINE to record line number LINE beginning at address ADDRESS
+   in the line table of subfile SUBFILE.  */
+
+static void
+dwarf_record_line (struct gdbarch *gdbarch, struct subfile *subfile,
+		   unsigned int line, CORE_ADDR address,
+		   record_line_ftype p_record_line)
+{
+  CORE_ADDR addr = gdbarch_addr_bits_remove (gdbarch, address);
+
+  (*p_record_line) (current_subfile, line, addr);
+}
+
+/* Subroutine of dwarf_decode_lines_1 to simplify it.
+   Mark the end of a set of line number records.
+   The arguments are the same as for dwarf_record_line.
+   If SUBFILE is NULL the request is ignored.  */
+
+static void
+dwarf_finish_line (struct gdbarch *gdbarch, struct subfile *subfile,
+		   CORE_ADDR address, record_line_ftype p_record_line)
+{
+  if (subfile != NULL)
+    dwarf_record_line (gdbarch, subfile, 0, address, p_record_line);
+}
+
 /* Subroutine of dwarf_decode_lines to simplify it.
    Process the line number information in LH.  */
 
@@ -17205,7 +17231,6 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
       unsigned int line = 1;
       int is_stmt = lh->default_is_stmt;
       int end_sequence = 0;
-      CORE_ADDR addr;
       unsigned char op_index = 0;
 
       if (!decode_for_pst_p && lh->num_file_names >= file)
@@ -17257,14 +17282,13 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
 		    {
 		      if (last_subfile != current_subfile)
 			{
-			  addr = gdbarch_addr_bits_remove (gdbarch, address);
-			  if (last_subfile)
-			    (*p_record_line) (last_subfile, 0, addr);
+			  dwarf_finish_line (gdbarch, last_subfile,
+					     address, p_record_line);
 			  last_subfile = current_subfile;
 			}
 		      /* Append row to matrix using current values.  */
-		      addr = gdbarch_addr_bits_remove (gdbarch, address);
-		      (*p_record_line) (current_subfile, line, addr);
+		      dwarf_record_line (gdbarch, current_subfile,
+					 line, address, p_record_line);
 		    }
 		}
 	    }
@@ -17357,13 +17381,12 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
 		    {
 		      if (last_subfile != current_subfile)
 			{
-			  addr = gdbarch_addr_bits_remove (gdbarch, address);
-			  if (last_subfile)
-			    (*p_record_line) (last_subfile, 0, addr);
+			  dwarf_finish_line (gdbarch, last_subfile,
+					     address, p_record_line);
 			  last_subfile = current_subfile;
 			}
-		      addr = gdbarch_addr_bits_remove (gdbarch, address);
-		      (*p_record_line) (current_subfile, line, addr);
+		      dwarf_record_line (gdbarch, current_subfile,
+					 line, address, p_record_line);
 		    }
 		}
 	      break;
@@ -17459,8 +17482,8 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
           lh->file_names[file - 1].included_p = 1;
           if (!decode_for_pst_p)
 	    {
-	      addr = gdbarch_addr_bits_remove (gdbarch, address);
-	      (*p_record_line) (current_subfile, 0, addr);
+	      dwarf_finish_line (gdbarch, current_subfile, address,
+				 p_record_line);
 	    }
         }
     }