gdb: use actual DWARF version in compunit's debugformat field

The "info source" command, with a DWARF-compile program, always show
that the debug info is "DWARF 2":

    (gdb) info source
    Current source file is test.c
    Compilation directory is /home/smarchi/build/binutils-gdb/gdb
    Located in /home/smarchi/build/binutils-gdb/gdb/test.c
    Contains 2 lines.
    Source language is c.
    Producer is GNU C17 9.3.0 -mtune=generic -march=x86-64 -g3 -gdwarf-5 -O0 -fasynchronous-unwind-tables -fstack-protector-strong -fstack-clash-protection -fcf-protection.
    Compiled with DWARF 2 debugging format.
    Includes preprocessor macro info.

Change it to display the actual DWARF version:

    (gdb) info source
    Current source file is test.c
    Compilation directory is /home/smarchi/build/binutils-gdb/gdb
    Located in /home/smarchi/build/binutils-gdb/gdb/test.c
    Contains 2 lines.
    Source language is c.
    Producer is GNU C17 9.3.0 -mtune=generic -march=x86-64 -g3 -gdwarf-5 -O0 -fasynchronous-unwind-tables -fstack-protector-strong -fstack-clash-protection -fcf-protection.
    Compiled with DWARF 5 debugging format.
    Includes preprocessor macro info.

The comp_unit_head::version field is guaranteed to be between 2 and 5,
thanks to the check in read_comp_unit_head.  So we can still use static
strings to pass to record_debugformat, and keep it efficient.

In the future, when somebody will update GDB to support DWARF 6, they'll
hit this assert and have to update this code.

Change-Id: I3270b7ebf5e9a17b4215405bd2e365662a4d6172

1 files changed, 12 insertions, 1 deletions

diff --git a/gdb/dwarf2/cu.c b/gdb/dwarf2/cu.c
index e7aed774c25..61981a45f8a 100644
--- a/gdb/dwarf2/cu.c
+++ b/gdb/dwarf2/cu.c
@@ -64,7 +64,18 @@ dwarf2_cu::start_symtab (const char *name, const char *comp_dir,
 
   list_in_scope = get_builder ()->get_file_symbols ();
 
-  get_builder ()->record_debugformat ("DWARF 2");
+  /* DWARF versions are restricted to [2, 5], thanks to the check in
+     read_comp_unit_head.  */
+  gdb_assert (this->header.version >= 2 && this->header.version <= 5);
+  static const char *debugformat_strings[] = {
+    "DWARF 2",
+    "DWARF 3",
+    "DWARF 4",
+    "DWARF 5",
+  };
+  const char *debugformat = debugformat_strings[this->header.version - 2];
+
+  get_builder ()->record_debugformat (debugformat);
   get_builder ()->record_producer (producer);
 
   processing_has_namespace_info = false;