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

1 files changed, 23 insertions, 3 deletions

diff --git a/gdb/dwarf2/line-header.h b/gdb/dwarf2/line-header.h
index 59b317d..32f52c4 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 */