libdw: Refactor dwarf_next_lines and fix skipped CU

dwarf_next_lines has two loops over CUs: one from the CU after the given
CU to the end, and one from the first CU up to _but not including_ the
given CU.  This means that the given CU is never checked.

This is unlikely to matter in practice since CUs usually correspond 1:1
with line number tables in the same order, but let's fix it anyways.
Refactoring it to one loop fixes the problem and simplifies the next
change to support DWARF package files.

	* libdw/dwarf_next_lines.c (dwarf_next_lines): Refactor loops
	over CUs into one loop.

Signed-off-by: Omar Sandoval <osandov@fb.com>

diff --git a/libdw/dwarf_next_lines.c b/libdw/dwarf_next_lines.c
index 74854ecdcf9d8d8eb90112fd952b0cf0ad75a9e8..6a9fe3610abb971f7d02cd52df525d7e8d3cd073 100644 (file)
--- a/libdw/dwarf_next_lines.c
+++ b/libdw/dwarf_next_lines.c
@@ -95,62 +95,49 @@ dwarf_next_lines (Dwarf *dbg, Dwarf_Off off,
     {
       /* We need to find the matching CU to get the comp_dir.  Use the
         given CU as hint where to start searching.  Normally it will
-        be the next CU that has a statement list. */
+        be the next CU that has a statement list.  If the CUs are in a
+        different order from the line tables, then we do a linear
+        search.  */
       Dwarf_CU *given_cu = *cu;
       Dwarf_CU *next_cu = given_cu;
-      bool found = false;
-      while (INTUSE(dwarf_get_units) (dbg, next_cu, &next_cu, NULL, NULL,
-                                     &cudie, NULL) == 0)
+      bool restarted = false;
+      while (1)
        {
-         if (dwarf_hasattr (&cudie, DW_AT_stmt_list))
+         if (restarted && next_cu == given_cu)
            {
-             Dwarf_Attribute attr;
-             Dwarf_Word stmt_off;
-             if (dwarf_formudata (dwarf_attr (&cudie, DW_AT_stmt_list, &attr),
-                                  &stmt_off) == 0
-                 && stmt_off == off)
-               {
-                 found = true;
-                 break;
-               }
+             /* We checked all of the CUs and there was no match.  */
+             *cu = NULL;
+             break;
            }
-         else if (off == 0
-                  && (next_cu->unit_type == DW_UT_split_compile
-                      || next_cu->unit_type == DW_UT_split_type))
+         if (INTUSE(dwarf_get_units) (dbg, next_cu, &next_cu, NULL, NULL,
+                                      &cudie, NULL) != 0)
            {
-             /* For split units (in .dwo files) there is only one table
-                at offset zero (containing just the files, no lines).  */
-             found = true;
-             break;
+             /* We didn't find the matching CU after the starting point.
+                Check the CUs up to the starting point.  */
+             next_cu = NULL;
+             restarted = true;
+             continue;
            }
-       }
 
-      if (!found && given_cu != NULL)
-       {
-         /* The CUs might be in a different order from the line
-            tables. Need to do a linear search (but stop at the given
-            CU, since we already searched those.  */
-         next_cu = NULL;
-         while (INTUSE(dwarf_get_units) (dbg, next_cu, &next_cu, NULL, NULL,
-                                         &cudie, NULL) == 0
-                && next_cu != given_cu)
+         Dwarf_Word stmt_off = 0;
+         if (dwarf_hasattr (&cudie, DW_AT_stmt_list))
            {
              Dwarf_Attribute attr;
-             Dwarf_Word stmt_off;
              if (dwarf_formudata (dwarf_attr (&cudie, DW_AT_stmt_list, &attr),
-                                  &stmt_off) == 0
-                 && stmt_off == off)
-               {
-                 found = true;
-                 break;
-               }
+                                  &stmt_off) != 0)
+               continue;
            }
-       }
+         /* Split units have an implicit offset of 0.  */
+         else if (next_cu->unit_type != DW_UT_split_compile
+                  && next_cu->unit_type != DW_UT_split_type)
+           continue;
 
-      if (found)
-       *cu = next_cu;
-      else
-       *cu = NULL;
+         if (stmt_off == off)
+           {
+             *cu = next_cu;
+             break;
+           }
+       }
     }
   else
     *cu = NULL;