[gdb/testsuite] Add -lbl option in gdb_test_multiple

Add gdb_test_multiple option -lbl, that adds a regexp after the user code that
reads one line, and discards it:
...
           -re "\r\n\[^\r\n\]*(?=\r\n)" {
               exp_continue
           }
...

In order to be able to write:
...
gdb_test_multiple "command" "testname" {
  ...
} -lbl
...
as opposed to having to insert the "" for the prompt_regexp arguments:
...
gdb_test_multiple "command" "testname" {
  ...
} "" -lbl
...
rewrite the promp_regexp argument usage into:
...
gdb_test_multiple "command" "testname" {
  ...
} -prompt $prompt_regexp
...

gdb/testsuite/ChangeLog:

2020-02-2120  Pedro Alves  <palves@redhat.com>
	      Tom de Vries  <tdevries@suse.de>

	* lib/gdb.exp (gdb_test_multiple): Handle prompt_regexp option using
	-prompt prefix.  Add -lbl option.
	(skip_python_tests_prompt, skip_libstdcxx_probe_tests_prompt)
	(gdb_is_target_1): Add -prompt prefix.
	* gdb.base/corefile-buildid.exp: Use -lbl option.  Rewrite regexps to
	have "\r\n" at start-of-line, instead of at end-of-line.

---
 gdb/testsuite/gdb.base/corefile-buildid.exp | 27 ++++++--------------------
 gdb/testsuite/lib/gdb.exp                   | 30 ++++++++++++++++++++++++-----
 2 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/gdb/testsuite/gdb.base/corefile-buildid.exp b/gdb/testsuite/gdb.base/corefile-buildid.exp
index b9844ee354..b91550bc82 100644
--- a/gdb/testsuite/gdb.base/corefile-buildid.exp
+++ b/gdb/testsuite/gdb.base/corefile-buildid.exp
@@ -114,17 +114,11 @@ proc check_exec_file {file} {
     # Get line with "Local exec file:".
     set ok 0
     gdb_test_multiple "info files" "" {
-	-re "^Local exec file:\r\n" {
+	-re "\r\nLocal exec file:" {
 	    set test_name $gdb_test_name
 	    set ok 1
 	}
-	-re "^$gdb_prompt $" {
-	    fail $gdb_test_name
-	}
-	-re "^\[^\r\n\]*\r\n" {
-	    exp_continue
-	}
-    }
+    } -lbl
 
     if { $ok == 0 } {
 	return
@@ -133,16 +127,10 @@ proc check_exec_file {file} {
     # Get subsequent line with $file.
     set ok 0
     gdb_test_multiple "" $test_name {
-	-re "^\[\t\ \]+`[string_to_regexp $file]'\[^\r\n\]*\r\n" {
+	-re "\r\n\[\t\ \]+`[string_to_regexp $file]'\[^\r\n\]*" {
 	    set ok 1
 	}
-	-re "^$gdb_prompt $" {
-	    fail $gdb_test_name
-	}
-	-re "^\[^\r\n\]*\r\n" {
-	    exp_continue
-	}
-    }
+    } -lbl
 
     if { $ok == 0 } {
 	return
@@ -150,13 +138,10 @@ proc check_exec_file {file} {
 
     # Skip till prompt.
     gdb_test_multiple "" $test_name {
-	-re "^$gdb_prompt $" {
+	-re "\r\n$gdb_prompt $" {
 	    pass $gdb_test_name
 	}
-	-re "^\[^\r\n\]*\r\n" {
-	    exp_continue
-	}
-    }
+    } -lbl
 }
 
 # Test whether gdb can find an exec file from a core file's build-id.
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 81518b9646..caa64f36f1 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -792,7 +792,7 @@ proc gdb_internal_error_resync {} {
 #	}
 #    }
 #
-proc gdb_test_multiple { command message user_code { prompt_regexp "" } } {
+proc gdb_test_multiple { command message user_code args } {
     global verbose use_gdb_stub
     global gdb_prompt pagination_prompt
     global GDB
@@ -802,6 +802,18 @@ proc gdb_test_multiple { command message user_code { prompt_regexp "" } } {
     upvar expect_out expect_out
     global any_spawn_id
 
+    set line_by_line 0
+    set prompt_regexp ""
+    for {set i 0} {$i < [llength $args]} {incr i} {
+	set opt [lindex $args $i]
+	if { $opt  == "-prompt" } {
+	    incr i
+	    set prompt_regexp [lindex $args $i]
+	} elseif { $opt == "-lbl" } {
+	    set line_by_line 1
+	}
+    }
+
     if { "$prompt_regexp" == "" } {
 	set prompt_regexp "$gdb_prompt $"
     }
@@ -1070,6 +1082,14 @@ proc gdb_test_multiple { command message user_code { prompt_regexp "" } } {
 	}
     }
 
+    if {$line_by_line} {
+       append code {
+           -re "\r\n\[^\r\n\]*(?=\r\n)" {
+               exp_continue
+           }
+       }
+    }
+
     # Now patterns that apply to any spawn id specified.
     append code {
 	-i $any_spawn_id
@@ -2005,7 +2025,7 @@ proc skip_python_tests_prompt { prompt_regexp } {
 	    return 1
 	}
 	-re "$prompt_regexp" {}
-    } "$prompt_regexp"
+    } -prompt "$prompt_regexp"
 
     gdb_test_multiple "python print (sys.version_info\[0\])" "check if python 3" {
 	-re "3.*$prompt_regexp" {
@@ -2014,7 +2034,7 @@ proc skip_python_tests_prompt { prompt_regexp } {
 	-re ".*$prompt_regexp" {
             set gdb_py_is_py3k 0
         }
-    } "$prompt_regexp"
+    } -prompt "$prompt_regexp"
 
     return 0
 }
@@ -3274,7 +3294,7 @@ proc skip_libstdcxx_probe_tests_prompt { prompt_regexp } {
 	}
 	-re "\r\n$prompt_regexp" {
 	}
-    } "$prompt_regexp"
+    } -prompt "$prompt_regexp"
     set skip [expr !$supported]
     return $skip
 }
@@ -3322,7 +3342,7 @@ proc gdb_is_target_1 { target_name target_stack_regexp prompt_regexp } {
 	-re "$prompt_regexp" {
 	    pass $test
 	}
-    } "$prompt_regexp"
+    } -prompt "$prompt_regexp"
     return 0
 }