gas/Dwarf: properly skip zero-size functions

PR gas/29451

While out_debug_abbrev() properly skips such functions, out_debug_info()
mistakenly didn't. It needs to calculate the high_pc expression ahead of
time, in order to skip emitting any data for the function if the value
is zero.

The one case which would still leave a zero-size entry is when
symbol_get_obj(symp)->size ends up evaluating to zero. I hope we can
expect that to not be the case, otherwise we'd need to have a way to
post-process .debug_info contents between resolving expressions and
actually writing the data out to the file. Even then it wouldn't be
entirely obvious in which way to alter the data.

diff --git a/gas/dwarf2dbg.c b/gas/dwarf2dbg.c
index 868ec79ee2cff6262a5ea2857633558936f846af..f346bd6a412e0ac549efee6ee6721c279b0cd581 100644 (file)
--- a/gas/dwarf2dbg.c
+++ b/gas/dwarf2dbg.c
@@ -2882,6 +2882,7 @@ out_debug_info (segT info_seg, segT abbrev_seg, segT line_seg, segT str_seg,
        {
          const char *name;
          size_t len;
+         expressionS size = { .X_op = O_constant };
 
          /* Skip warning constructs (see above).  */
          if (symbol_get_bfdsym (symp)->flags & BSF_WARNING)
@@ -2895,6 +2896,18 @@ out_debug_info (segT info_seg, segT abbrev_seg, segT line_seg, segT str_seg,
          if (!S_IS_DEFINED (symp) || !S_IS_FUNCTION (symp))
            continue;
 
+#if defined (OBJ_ELF) /* || defined (OBJ_MAYBE_ELF) */
+         size.X_add_number = S_GET_SIZE (symp);
+         if (size.X_add_number == 0 && IS_ELF
+             && symbol_get_obj (symp)->size != NULL)
+           {
+             size.X_op = O_add;
+             size.X_op_symbol = make_expr_symbol (symbol_get_obj (symp)->size);
+           }
+#endif
+         if (size.X_op == O_constant && size.X_add_number == 0)
+           continue;
+
          subseg_set (str_seg, 0);
          name_sym = symbol_temp_new_now_octets ();
          name = S_GET_NAME (symp);
@@ -2920,29 +2933,17 @@ out_debug_info (segT info_seg, segT abbrev_seg, segT line_seg, segT str_seg,
          emit_expr (&exp, sizeof_address);
 
          /* DW_AT_high_pc */
-         exp.X_op = O_constant;
-#if defined (OBJ_ELF) /* || defined (OBJ_MAYBE_ELF) */
-         exp.X_add_number = S_GET_SIZE (symp);
-         if (exp.X_add_number == 0 && IS_ELF
-             && symbol_get_obj (symp)->size != NULL)
-           {
-             exp.X_op = O_add;
-             exp.X_op_symbol = make_expr_symbol (symbol_get_obj (symp)->size);
-           }
-#else
-         exp.X_add_number = 0;
-#endif
          if (DWARF2_VERSION < 4)
            {
-             if (exp.X_op == O_constant)
-               exp.X_op = O_symbol;
-             exp.X_add_symbol = symp;
-             emit_expr (&exp, sizeof_address);
+             if (size.X_op == O_constant)
+               size.X_op = O_symbol;
+             size.X_add_symbol = symp;
+             emit_expr (&size, sizeof_address);
            }
-         else if (exp.X_op == O_constant)
-           out_uleb128 (exp.X_add_number);
+         else if (size.X_op == O_constant)
+           out_uleb128 (size.X_add_number);
          else
-           emit_leb128_expr (symbol_get_value_expression (exp.X_op_symbol), 0);
+           emit_leb128_expr (symbol_get_value_expression (size.X_op_symbol), 0);
        }
 
       /* End of children.  */