[gdb/symtab] Fix version check in dwarf compilation unit header

The version check of the dwarf compilation unit header in
error_check_comp_unit_head is done too late, and consequently dwarf code with
an unsupported version in the compilation unit header is interpreted as dwarf5
code in read_comp_unit_head.

Fixed by moving the check earlier.

Build and reg-tested on x86_64-linux.

2018-07-04  Tom de Vries  <tdevries@suse.de>

	* dwarf2read.c (error_check_comp_unit_head): Move dwarf version
	check ...
	(read_comp_unit_head): ... here.

	* gdb.dwarf2/dw2-error.exp: Update expected error message.

Author: vries

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2018-07-04  Tom de Vries  <tdevries@suse.de>
+
+	* dwarf2read.c (error_check_comp_unit_head): Move dwarf version
+	check ...
+	(read_comp_unit_head): ... here.
+
 2018-07-03  Tom Tromey  <tom@tromey.com>
 
 	* tracepoint.c (process_tracepoint_on_disconnect, start_tracing)

gdb/dwarf2read.c

@@ -6308,6 +6308,10 @@ read_comp_unit_head (struct comp_unit_head *cu_header,
   cu_header->offset_size = (bytes_read == 4) ? 4 : 8;
   info_ptr += bytes_read;
   cu_header->version = read_2_bytes (abfd, info_ptr);
+  if (cu_header->version < 2 || cu_header->version > 5)
+    error (_("Dwarf Error: wrong version in compilation unit header "
+	   "(is %d, should be 2, 3, 4 or 5) [in module %s]"),
+	   cu_header->version, filename);
   info_ptr += 2;
   if (cu_header->version < 5)
     switch (section_kind)
@@ -6410,11 +6414,6 @@ error_check_comp_unit_head (struct dwarf2_per_objfile *dwarf2_per_objfile,
 {
   const char *filename = get_section_file_name (section);
 
-  if (header->version < 2 || header->version > 5)
-    error (_("Dwarf Error: wrong version in compilation unit header "
-	   "(is %d, should be 2, 3, 4 or 5) [in module %s]"), header->version,
-	   filename);
-
   if (to_underlying (header->abbrev_sect_off)
       >= dwarf2_section_size (dwarf2_per_objfile->objfile, abbrev_section))
     error (_("Dwarf Error: bad offset (%s) in compilation unit header "

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2018-07-04  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.dwarf2/dw2-error.exp: Update expected error message.
+
 2018-07-02  Maciej W. Rozycki  <macro@mips.com>
 
 	PR tdep/8282

gdb/testsuite/gdb.dwarf2/dw2-error.exp

@@ -41,7 +41,7 @@ gdb_test_no_output "set breakpoint pending off"
 
 # First test that reading symbols fails.
 gdb_test "file $binfile" \
-    {Reading symbols.*Dwarf Error: wrong unit_type in compilation unit header \(is 0, should be 1 or 2\).*} \
+    {Reading symbols.*Dwarf Error: wrong version in compilation unit header \(is 153, should be 2, 3, 4 or 5\).*} \
     "file $testfile"
 
 # Now check that we can still break given the minimal symbol.