gdb/dwarf: pass compilation directory to line header

The following patch changes line_header::file_file_name to prepend the
compilation directory to the file name, if needed.  For that, the line
header needs to know about the compilation directory.  Prepare for that
by adding a constructor that takes it as a parameter, and passing the
value down everywhere needed.  Add a second constructor for the special
case of building a line_header for doing a hash table lookup, since that
case doesn't require a compilation directory value.

Change-Id: Iba3ba0293e4e2d13a64b257cf9a3094684d54330

3 files changed, 41 insertions, 17 deletions

diff --git a/gdb/dwarf2/line-header.c b/gdb/dwarf2/line-header.c
index 6323084756..13379851b9 100644
--- a/gdb/dwarf2/line-header.c
+++ b/gdb/dwarf2/line-header.c
@@ -264,7 +264,8 @@ line_header_up
 dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
 			   dwarf2_per_objfile *per_objfile,
 			   struct dwarf2_section_info *section,
-			   const struct comp_unit_head *cu_header)
+			   const struct comp_unit_head *cu_header,
+			   const char *comp_dir)
 {
   const gdb_byte *line_ptr;
   unsigned int bytes_read, offset_size;
@@ -281,7 +282,7 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
       return 0;
     }
 
-  line_header_up lh (new line_header ());
+  line_header_up lh (new line_header (comp_dir));
 
   lh->sect_off = sect_off;
   lh->offset_in_dwz = is_dwz;
diff --git a/gdb/dwarf2/line-header.h b/gdb/dwarf2/line-header.h
index 59b317d0d7..32f52c4a64 100644
--- a/gdb/dwarf2/line-header.h
+++ b/gdb/dwarf2/line-header.h
@@ -68,8 +68,18 @@ struct file_entry
    which contains the following information.  */
 struct line_header
 {
-  line_header ()
-    : offset_in_dwz {}
+  /* COMP_DIR is the value of the DW_AT_comp_dir attribute of the compilation
+     unit in the context of which we are reading this line header, or nullptr
+     if unknown or not applicable.  */
+  explicit line_header (const char *comp_dir)
+    : offset_in_dwz {}, m_comp_dir (comp_dir)
+  {}
+
+  /* This constructor should only be used to create line_header intances to do
+     hash table lookups.  */
+  line_header (sect_offset sect_off, bool offset_in_dwz)
+    : sect_off (sect_off),
+      offset_in_dwz (offset_in_dwz)
   {}
 
   /* Add an entry to the include directory table.  */
@@ -161,6 +171,11 @@ struct line_header
      number FILE in this object's file name table.  */
   std::string file_file_name (int file) const;
 
+  /* Return the compilation directory of the compilation unit in the context of
+     which this line header is read.  Return nullptr if non applicable.  */
+  const char *comp_dir () const
+  { return m_comp_dir; }
+
  private:
   /* The include_directories table.  Note these are observing
      pointers.  The memory is owned by debug_line_buffer.  */
@@ -171,6 +186,10 @@ struct line_header
      before, and is 0 in DWARF 5 and later).  So the client should use
      file_name_at method for access.  */
   std::vector<file_entry> m_file_names;
+
+  /* Compilation directory of the compilation unit in the context of which this
+     line header is read.  nullptr if unknown or not applicable.  */
+  const char *m_comp_dir = nullptr;
 };
 
 typedef std::unique_ptr<line_header> line_header_up;
@@ -191,6 +210,7 @@ file_entry::include_dir (const line_header *lh) const
 
 extern line_header_up dwarf_decode_line_header
   (sect_offset sect_off, bool is_dwz, dwarf2_per_objfile *per_objfile,
-   struct dwarf2_section_info *section, const struct comp_unit_head *cu_header);
+   struct dwarf2_section_info *section, const struct comp_unit_head *cu_header,
+   const char *comp_dir);
 
 #endif /* DWARF2_LINE_HEADER_H */
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 70419da13e..b6d9f5a8aa 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -949,7 +949,8 @@ static struct die_info *die_specification (struct die_info *die,
 					   struct dwarf2_cu **);
 
 static line_header_up dwarf_decode_line_header (sect_offset sect_off,
-						struct dwarf2_cu *cu);
+						struct dwarf2_cu *cu,
+						const char *comp_dir);
 
 static void dwarf_decode_lines (struct line_header *,
 				struct dwarf2_cu *,
@@ -2746,6 +2747,8 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,
   line_header_up lh;
   sect_offset line_offset {};
 
+  file_and_directory &fnd = find_file_and_directory (comp_unit_die, cu);
+
   attr = dwarf2_attr (comp_unit_die, DW_AT_stmt_list, cu);
   if (attr != nullptr && attr->form_is_unsigned ())
     {
@@ -2765,11 +2768,9 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,
 	  return;
 	}
 
-      lh = dwarf_decode_line_header (line_offset, cu);
+      lh = dwarf_decode_line_header (line_offset, cu, fnd.get_comp_dir ());
     }
 
-  file_and_directory &fnd = find_file_and_directory (comp_unit_die, cu);
-
   int offset = 0;
   if (!fnd.is_unknown ())
     ++offset;
@@ -9451,11 +9452,11 @@ find_file_and_directory (struct die_info *die, struct dwarf2_cu *cu)
 
 static void
 handle_DW_AT_stmt_list (struct die_info *die, struct dwarf2_cu *cu,
+			const file_and_directory &fnd,
 			CORE_ADDR lowpc) /* ARI: editCase function */
 {
   dwarf2_per_objfile *per_objfile = cu->per_objfile;
   struct attribute *attr;
-  struct line_header line_header_local;
   hashval_t line_header_local_hash;
   void **slot;
   int decode_mapping;
@@ -9484,8 +9485,7 @@ handle_DW_AT_stmt_list (struct die_info *die, struct dwarf2_cu *cu,
 				   xcalloc, xfree));
     }
 
-  line_header_local.sect_off = line_offset;
-  line_header_local.offset_in_dwz = cu->per_cu->is_dwz;
+  line_header line_header_local (line_offset, cu->per_cu->is_dwz);
   line_header_local_hash = line_header_hash (&line_header_local);
   if (per_objfile->line_header_hash != NULL)
     {
@@ -9506,7 +9506,8 @@ handle_DW_AT_stmt_list (struct die_info *die, struct dwarf2_cu *cu,
 
   /* dwarf_decode_line_header does not yet provide sufficient information.
      We always have to call also dwarf_decode_lines for it.  */
-  line_header_up lh = dwarf_decode_line_header (line_offset, cu);
+  line_header_up lh = dwarf_decode_line_header (line_offset, cu,
+						fnd.get_comp_dir ());
   if (lh == NULL)
     return;
 
@@ -9584,7 +9585,7 @@ read_file_scope (struct die_info *die, struct dwarf2_cu *cu)
      lnp_state_machine::check_line_address) will fail to properly
      exclude an entry that was removed via --gc-sections.  */
   if (lowpc != highpc)
-    handle_DW_AT_stmt_list (die, cu, lowpc);
+    handle_DW_AT_stmt_list (die, cu, fnd, lowpc);
 
   /* Process all dies in compilation unit.  */
   if (die->child != NULL)
@@ -9658,7 +9659,7 @@ dwarf2_cu::setup_type_unit_groups (struct die_info *die)
   if (attr != NULL && attr->form_is_unsigned ())
     {
       sect_offset line_offset = (sect_offset) attr->as_unsigned ();
-      lh = dwarf_decode_line_header (line_offset, this);
+      lh = dwarf_decode_line_header (line_offset, this, nullptr);
     }
   if (lh == NULL)
     {
@@ -19739,7 +19740,8 @@ get_debug_line_section (struct dwarf2_cu *cu)
    and must not be freed.  */
 
 static line_header_up
-dwarf_decode_line_header (sect_offset sect_off, struct dwarf2_cu *cu)
+dwarf_decode_line_header (sect_offset sect_off, struct dwarf2_cu *cu,
+			  const char *comp_dir)
 {
   struct dwarf2_section_info *section;
   dwarf2_per_objfile *per_objfile = cu->per_objfile;
@@ -19756,7 +19758,8 @@ dwarf_decode_line_header (sect_offset sect_off, struct dwarf2_cu *cu)
     }
 
   return dwarf_decode_line_header (sect_off, cu->per_cu->is_dwz,
-				   per_objfile, section, &cu->header);
+				   per_objfile, section, &cu->header,
+				   comp_dir);
 }
 
 /* Subroutine of dwarf_decode_lines to simplify it.