[gdb/testsuite] Fix handling of nr_args < 3 in mi_gdb_test

The documentation of mi_gdb_test states that the command, pattern and message
arguments are mandatory:
...
 # mi_gdb_test COMMAND PATTERN MESSAGE [IPATTERN] -- send a command to gdb;
 #   test the result.
...

However, this is not checked, and when mi_gdb_test is called with less than 3
arguments, it passes or fails silently.

Fix this by using the following semantics:
- if there are 1 or 2 arguments, use the command as the message.
- if there is 1 argument, use ".*" as the pattern.
- if there are no or too much arguments, error out.

Fix a PATH issue in gdb.mi/mi-logging.exp, introduced by using the command as
message.  Fix a few other trivial-looking FAILs.

There are 11 less trivial-looking FAILs left in gdb.mi in test-cases:
- mi-nsmoribund.exp
- mi-breakpoint-changed.exp
- mi-break.exp.

Tested on x86_64-linux.

gdb/testsuite/gdb.mi/mi-break.exp

@@ -341,7 +341,7 @@ proc_with_prefix test_explicit_breakpoints {} {
 
     # First check mixed explicit/parsed linespecs.
     mi_gdb_test "-break-insert --function main $srcfile:$line_callee3_head" \
-	".*Garbage following explicit linespec"
+	".*Garbage following explicit location.*"
 
     # Insert some breakpoints and list them
     # Also, disable some so they do not interfere with other tests

gdb/testsuite/gdb.mi/mi-logging.exp

@@ -32,7 +32,8 @@ if {[mi_runto_main] < 0} {
 
 set milogfile [standard_output_file "milog.txt"]
 
-mi_gdb_test "-gdb-set logging file $milogfile" ".*"
+mi_gdb_test "-gdb-set logging file $milogfile" "\\^done" \
+    "-gdb-set logging file"
 
 mi_gdb_test "-gdb-set logging overwrite on" ".*"
 

gdb/testsuite/gdb.mi/mi-memory-changed.exp

@@ -75,7 +75,8 @@ gdb_expect {
     }
 }
 
-mi_gdb_test "set var *(unsigned int *) ${main_addr} = ${main_insn}" \
-    ".*=memory-changed,thread-group=\"i${decimal}\".addr=\"${main_addr}\",len=\"0x4\",type=\"code\".*\\^done"
+regsub ^0x0* $main_addr "" main_addr
+mi_gdb_test "set var *(unsigned int *) 0x${main_addr} = ${main_insn}" \
+    ".*=memory-changed,thread-group=\"i${decimal}\".addr=\"0x0*${main_addr}\",len=\"0x4\",type=\"code\".*\\^done"
 mi_gdb_exit
 return 0

gdb/testsuite/gdb.mi/mi-nsmoribund.exp

@@ -115,7 +115,12 @@ mi_check_thread_states \
 # gdb_test_multiple (or an MI equivalent)
 
 mi_gdb_test "102-break-delete" "102\\^done.*"
-mi_gdb_test "print done = 1" { = 1"}
+set re [list \
+	    [string_list_to_regexp ~ {"} $] \
+	    $decimal \
+	    [string_list_to_regexp " = 1" \\ n {"} \r\n ^ done]]
+set re [join $re ""]
+mi_gdb_test "print done = 1" $re
 mi_gdb_test "103-exec-continue --all" "\[^\n\]*\r\n$running_re"
 
 gdb_expect {

gdb/testsuite/gdb.python/py-mi.exp

@@ -44,7 +44,9 @@ mi_runto_main
 
 set remote_python_file [gdb_remote_download host ${srcdir}/${subdir}/${pyfile}]
 
-mi_gdb_test "source ${remote_python_file}" "load python file"
+set cmd "source ${remote_python_file}"
+set re [string_list_to_regexp & {"} $cmd \\ n {"} \r\n ^ done]
+mi_gdb_test $cmd $re "load python file"
 
 mi_continue_to_line [gdb_get_line_number {MI breakpoint here} ${srcfile}] \
   "step to breakpoint"
@@ -74,7 +76,7 @@ with_test_prefix "varobj nscont" {
     mi_delete_varobj nscont "delete varobj"
 }
 
-mi_gdb_test "-enable-pretty-printing" ""
+mi_gdb_test "-enable-pretty-printing" "\\^done"
 
 mi_create_varobj_checked string string_1 \
     "struct string_repr" \
@@ -283,7 +285,9 @@ with_test_prefix "varobj nscont" {
 	"choose default visualizer"
 }
 
-mi_gdb_test "python exception_flag = True" ""
+set cmd "python exception_flag = True"
+set re [string_list_to_regexp & {"} $cmd \\ n {"} \r\n ^ done]
+mi_gdb_test $cmd $re
 
 mi_create_dynamic_varobj nstype2 nstype2 1 \
   "create nstype2 varobj"

gdb/testsuite/lib/mi-support.exp

@@ -691,16 +691,18 @@ proc mi_readnow { args } {
     return $readnow_p
 }
 
-# mi_gdb_test COMMAND PATTERN MESSAGE [IPATTERN] -- send a command to gdb; 
+# mi_gdb_test COMMAND [PATTERN [MESSAGE [IPATTERN]]] -- send a command to gdb;
 #   test the result.
 #
 # COMMAND is the command to execute, send to GDB with send_gdb.  If
 #   this is the null string no command is sent.
 # PATTERN is the pattern to match for a PASS, and must NOT include
 #   the \r\n sequence immediately before the gdb prompt.
+#   If not specified, .* is used.
 # MESSAGE is the message to be printed.  (If this is the empty string,
 #   then sometimes we don't call pass or fail at all; I don't
 #   understand this at all.)
+#   If not specified, COMMAND is used.
 # IPATTERN is the pattern to match for the inferior's output.  This parameter
 #   is optional.  If present, it will produce a PASS if the match is
 #   successful, and a FAIL if unsuccessful.
@@ -717,9 +719,23 @@ proc mi_gdb_test { args } {
     global inferior_exited_re async
     upvar timeout timeout
 
-    set command [lindex $args 0]
-    set pattern [lindex $args 1]
-    set message [lindex $args 2]
+    if { [llength $args] >= 1 } then {
+	set command [lindex $args 0]
+    } else {
+	error "Not enough arguments in mi_gdb_test"
+    }
+
+    if { [llength $args] >= 2 } then {
+	set pattern [lindex $args 1]
+    } else {
+	set pattern ".*"
+    }
+
+    if { [llength $args] >= 3 } then {
+	set message [lindex $args 2]
+    } else {
+	set message $command
+    }
 
     if [llength $args]==4 {
 	set ipattern [lindex $args 3]
@@ -732,6 +748,10 @@ proc mi_gdb_test { args } {
 	set question_string "^FOOBAR$"
     }
 
+    if { [llength $args] >= 6 } {
+	error "Too many arguments in mi_gdb_test"
+    }
+
     if $verbose>2 then {
 	send_user "Sending \"$command\" to gdb\n"
 	send_user "Looking to match \"$pattern\"\n"