gdb: Allow quoting around string options in the gdb::option framework

Currently string options must be a single string with no whitespace,
this limitation prevents the gdb::option framework being used in some
places.

After this commit, string options can be quoted in single or double
quotes, and quote characters can be escaped with a backslash if needed
to either place them within quotes, or to avoid starting a quoted
argument.

This test adds a new function extract_string_maybe_quoted which is
basically a copy of extract_arg_maybe_quoted from cli/cli-utils.c,
however, the cli-utils.c function will be deleted in the next commit.

There are tests to exercise the new quoting mechanism.

gdb/ChangeLog:

	* cli/cli-option.c (parse_option): Use extract_string_maybe_quoted
	to extract string arguments.
	* common/common-utils.c (extract_string_maybe_quoted): New function.
	* common/common-utils.h (extract_string_maybe_quoted): Declare.

gdb/testsuite/ChangeLog:

	* gdb.base/options.exp (expect_string): Dequote strings in
	results.
	(test-string): Test strings with different quoting and reindent.

1 files changed, 2 insertions, 3 deletions

diff --git a/gdb/cli/cli-option.c b/gdb/cli/cli-option.c
index 07d552b..eb8ef79 100644
--- a/gdb/cli/cli-option.c
+++ b/gdb/cli/cli-option.c
@@ -434,13 +434,12 @@ parse_option (gdb::array_view<const option_def_group> options_group,
 	  }
 
 	const char *arg_start = *args;
-	*args = skip_to_space (*args);
-
+	std::string str = extract_string_maybe_quoted (args);
 	if (*args == arg_start)
 	  error (_("-%s requires an argument"), match->name);
 
 	option_value val;
-	val.string = savestring (arg_start, *args - arg_start);
+	val.string = xstrdup (str.c_str ());
 	return option_def_and_value {*match, match_ctx, val};
       }