Add "style" proc to the test suite

This adds a "style" helper proc to the test suite, and updates
existing style tests to use it.  Thanks to Sergio for the idea.

Tested on x86-64 Fedora 29.

gdb/testsuite/ChangeLog
2019-05-22  Tom Tromey  <tromey@adacore.com>

	* gdb.base/info-shared.exp (check_info_shared): Use "style".
	* gdb.base/style.exp: Use "style".
	* lib/gdb-utils.exp (style): New proc.

diff --git a/gdb/testsuite/gdb.base/style.exp b/gdb/testsuite/gdb.base/style.exp
--- a/gdb/testsuite/gdb.base/style.exp
+++ b/gdb/testsuite/gdb.base/style.exp
@@ -41,10 +41,10 @@ save_vars { env(TERM) } {
 
     gdb_test_no_output "set style enabled on"
 
-    set main_expr "\033\\\[33mmain\033\\\[m"
-    set base_file_expr "\033\\\[32m.*style\\.c\033\\\[m"
+    set main_expr [style main function]
+    set base_file_expr [style ".*style\\.c" file]
     set file_expr "$base_file_expr:\[0-9\]"
-    set arg_expr "\033\\\[36marg.\033\\\[m"
+    set arg_expr [style "arg." variable]
 
     gdb_test "frame" \
 	"$main_expr.*$arg_expr.*$arg_expr.*$file_expr.*"
@@ -58,7 +58,7 @@ save_vars { env(TERM) } {
 
     gdb_test "break main" "file $base_file_expr.*"
 
-    gdb_test "print &main" " = .* \033\\\[34m$hex\033\\\[m <$main_expr>"
+    gdb_test "print &main" " = .* [style $hex address] <$main_expr>"
 
     # Regression test for a bug where line-wrapping would occur at the
     # wrong spot with styling.  There were different bugs at different
@@ -86,11 +86,12 @@ save_vars { env(TERM) } {
     gdb_exit
     gdb_spawn
 
-    gdb_test "" "\033\\\[35;1mGNU gdb.*\033\\\[m.*" \
+    set vers [style "GNU gdb.*" "35;1"]
+    gdb_test "" "${vers}.*" \
 	"version is styled"
 
     set quoted [string_to_regexp $binfile]
     gdb_test "file $binfile" \
-	"Reading symbols from \033\\\[32m${quoted}\033\\\[m..." \
+	"Reading symbols from [style $quoted file]..." \
 	"filename is styled when loading symbol file"
 }
diff --git a/gdb/testsuite/lib/gdb-utils.exp b/gdb/testsuite/lib/gdb-utils.exp
--- a/gdb/testsuite/lib/gdb-utils.exp
+++ b/gdb/testsuite/lib/gdb-utils.exp
@@ -37,3 +37,21 @@ proc string_to_regexp {str} {
     regsub -all {[]*+.|(){}^$\[\\]} $str {\\&} result
     return $result
 }
+
+# Wrap STR in an ANSI terminal escape sequences -- one to set the
+# style to STYLE, and one to reset the style to the default.  The
+# return value is suitable for use as a regular expression.
+
+# STYLE can either be the payload part of an ANSI terminal sequence,
+# or a shorthand for one of the gdb standard styles: "file",
+# "function", "variable", or "address".
+
+proc style {str style} {
+    switch -exact -- $style {
+	file { set style 32 }
+	function { set style 33 }
+	variable { set style 36 }
+	address { set style 34 }
+    }
+    return "\033\\\[${style}m${str}\033\\\[m"
+}

