gdb/linespec: relax the position of the '-force-condition' flag

The break command's "-force-condition" flag is currently required to
be followed by the "if" keyword.  This prevents flexibility when using
other keywords, e.g. "thread":

  (gdb) break main -force-condition thread 1 if foo
  Function "main -force-condition" not defined.
  Make breakpoint pending on future shared library load? (y or [n]) n

Remove the requirement that "-force-condition" is always followed by
an "if", so that more flexibility is obtained when positioning
keywords.

gdb/ChangeLog:
2020-12-07  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* linespec.c (linespec_lexer_lex_keyword): The "-force-condition"
	keyword may be followed by any keyword.
	* breakpoint.c (find_condition_and_thread): Advance 'tok' by
	'toklen' in the case for "-force-condition".

gdb/testsuite/ChangeLog:
2020-12-07  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* gdb.linespec/keywords.exp: Add tests to check positional
	flexibility of "-force-condition".

1 files changed, 12 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.linespec/keywords.exp b/gdb/testsuite/gdb.linespec/keywords.exp
index 93bdcc9..645f44f 100644
--- a/gdb/testsuite/gdb.linespec/keywords.exp
+++ b/gdb/testsuite/gdb.linespec/keywords.exp
@@ -75,3 +75,15 @@ gdb_test "break task task 123" "Unknown task 123\\."
 # Test NULL location with valid conditional containing a keyword.
 gdb_breakpoint "thread if thread == 0"
 gdb_breakpoint "task if task == 0"
+
+# Test the positional flexibility of the "-force-condition" flag.
+foreach prefix {"" "thread 1 "} {
+    foreach suffix {"" " " " thread 1"} {
+	foreach cond {"" " if 1"} {
+	    with_test_prefix "prefix: '$prefix', suffix: '$suffix', cond: '$cond'" {
+		gdb_breakpoint "main ${prefix}-force-condition${suffix}${cond}"\
+		    "message"
+	    }
+	}
+    }
+}