Fix timeout with maint print objfiles

I'm seeing timeouts from gdb.rust/traits.exp when we attempt to print
things with "maint print objfiles".

This happens for two reasons:

1 - GDB does not explicitly split each entry into its own line, but rather
    relies on the terminal's width to insert line breaks.

2 - When running the GDB testsuite, such width may be unlimited, which will
    prevent GDB from inserting any line breaks.

As a result, the output may be too lengthy and will come in big lines.  Tweak
the support library to match the patterns line-by-line, which gives us more
time to match things. Also fix GDB's output to print one entry per line,
regardless of the terminal width.

A similar approach was used in another testcase using the same command (commit
eaeaf44cfd). With the new line breaks, we don't
need a particular pattern, so clean up that test as well.

gdb/ChangeLog:

2021-04-27  Luis Machado  <luis.machado@linaro.org>

	* psymtab.c (psymbol_functions::dump): Output newline.
	* symmisc.c (dump_objfile): Likewise.

gdb/testsuite/ChangeLog:

2021-04-27  Luis Machado  <luis.machado@linaro.org>

	* gdb.base/maint.exp: Drop a pattern that is not needed.
	* lib/gdb.exp (readnow): Match line-by-line.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2021-04-27  Luis Machado  <luis.machado@linaro.org>
+
+	* psymtab.c (psymbol_functions::dump): Output newline.
+	Remove wrap.
+	* symmisc.c (dump_objfile): Likewise.
+
 2021-04-27  Michael Weghorn  <m.weghorn@posteo.de>
 	    Simon Marchi  <simon.marchi@polymtl.ca>
 

gdb/psymtab.c

@@ -885,8 +885,7 @@ psymbol_functions::dump (struct objfile *objfile)
 	  printf_filtered ("%s at ",
 			   psymtab->filename);
 	  gdb_print_host_address (psymtab, gdb_stdout);
-	  printf_filtered (", ");
-	  wrap_here ("  ");
+	  printf_filtered ("\n");
 	}
       printf_filtered ("\n\n");
     }

gdb/symmisc.c

@@ -131,12 +131,9 @@ dump_objfile (struct objfile *objfile)
 	      printf_filtered ("%s at ",
 			       symtab_to_filename_for_display (symtab));
 	      gdb_print_host_address (symtab, gdb_stdout);
-	      printf_filtered (", ");
 	      if (SYMTAB_OBJFILE (symtab) != objfile)
-		{
-		  printf_filtered ("NOT ON CHAIN!  ");
-		}
-	      wrap_here ("  ");
+		printf_filtered (", NOT ON CHAIN!");
+	      printf_filtered ("\n");
 	    }
 	}
       printf_filtered ("\n\n");

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2021-04-27  Luis Machado  <luis.machado@linaro.org>
+
+	* gdb.base/maint.exp: Drop a pattern that is not needed.
+	* lib/gdb.exp (readnow): Match line-by-line.
+
 2021-04-27  Luis Machado  <luis.machado@linaro.org>
 
 	* gdb.xml/tdesc-reload.exp: Pass -lbl.

gdb/testsuite/gdb.base/maint.exp

@@ -230,9 +230,6 @@ gdb_test_multiple "maint print objfiles" "" -lbl {
 	set symtabs 1
 	exp_continue
     }
-    -re " at $hex," {
-	exp_continue
-    }
     -re -wrap "" {
 	pass $gdb_test_name
     }

gdb/testsuite/lib/gdb.exp

@@ -7511,17 +7511,24 @@ proc readnow { args } {
     } else {
 	set re ""
     }
+
+    set readnow_p 0
+    # Given the listing from the following command can be very verbose, match
+    # the patterns line-by-line.  This prevents timeouts from waiting for
+    # too much data to come at once.
     set cmd "maint print objfiles $re"
-    gdb_test_multiple $cmd "" {
-	-re -wrap "\r\n.gdb_index: faked for \"readnow\"\r\n.*" {
-	    return 1
+    gdb_test_multiple $cmd "" -lbl {
+	-re "\r\n.gdb_index: faked for \"readnow\"" {
+	    # Record the we've seen the above pattern.
+	    set readnow_p 1
+	    exp_continue
 	}
 	-re -wrap "" {
-	    return 0
+	    # We don't care about any other input.
 	}
     }
 
-    return 0
+    return $readnow_p
 }
 
 # Return 1 if partial symbols are available.  Otherwise, return 0.