Re: [PATCH] allow empty string as argument to -Map

[Nick Clifton <nickc@redhat.com>]

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Hi Rasmus,

> That makes a lot of sense, thanks. And one can get "my" behaviour by
> passing "-Map=." or "-Map .", 

Ha!  I had not even though of that.

> ... eliminates the somewhat clumsy need to specify the empty string as
> argument, 

Agreed.

> So before this gets set in stone, can I retract my suggestion of
> assigning meaning to the empty string (maybe continue to handle it
> internally equivalent to ".", but not advertising it)?

I have made the change.  See the attached patch.  I decided that for
the empty string case it would be best to generate a message telling
the user and ignoring the map file request.


> (And perhaps change "map file" to "link map" or "linker map")

Also done.

Cheers
  Nick

ld/ChangeLog
2020-05-28  Nick Clifton  <nickc@redhat.com>

	* lexsup.c (parse_args): Generate an error if a name is not
	provided to the -Map option.
	(ld_options): Mention that the -Map option supports a directory
	name as an argument.
	* NEWS: Remove mention of support for an empty string as an
	argument to -Map.
	* ld.texi: Likewise.

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diff --git a/ld/NEWS b/ld/NEWS
index 98f07a73e1..2240aeb788 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -1,9 +1,8 @@
 -*- text -*-
 
 * The -Map=<filename> command line option has been extended so that if
-  <filename> is omitted then a file called <output-filename>.map will be
-  created.  Plus if <filename> is a directory then
-  <filename>/<output-filename>.map will be created.
+  <filename> is a directory then <filename>/<output-filename>.map will be
+  created.
 
 * Add a command-line option for ELF linker, --warn-textrel, to warn that
   DT_TEXTREL is set in a position-independent executable or shared object.
diff --git a/ld/ld.texi b/ld/ld.texi
index 52342523ed..cb38f47cd3 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -1760,12 +1760,10 @@ Print a summary of all target-specific options on the standard output and exit.
 @kindex -Map=@var{mapfile}
 @item -Map=@var{mapfile}
 Print a link map to the file @var{mapfile}.  See the description of the
-@option{-M} option, above.  Specifying the empty string as @var{mapfile}
-(that is, @code{-Map=}) causes the link map to be written to a file
-named after the @var{output} file, with @code{.map} appended.
-Specifying a directory as @var{mapfile} causes the link map to be
-written into a file inside the directory.  The name of the file is
-again based upon the @var{output} filename with @code{.map} appended.
+@option{-M} option, above.  Specifying a directory as @var{mapfile}
+causes the linker map to be written into a file inside the directory.
+The name of the file is based upon the @var{output} filename with
+@code{.map} appended.
 
 @cindex memory usage
 @kindex --no-keep-memory
diff --git a/ld/lexsup.c b/ld/lexsup.c
index 49c4f23950..781f58aff7 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -359,7 +359,7 @@ static const struct ld_option ld_options[] =
   { {"init", required_argument, NULL, OPTION_INIT},
     '\0', N_("SYMBOL"), N_("Call SYMBOL at load-time"), ONE_DASH },
   { {"Map", required_argument, NULL, OPTION_MAP},
-    '\0', N_("[FILE]"), N_("Write a map file (default: <outputname>.map)"), ONE_DASH },
+    '\0', N_("FILE/DIR"), N_("Write a linker map to FILE or DIR/<outputname>.map"), ONE_DASH },
   { {"no-define-common", no_argument, NULL, OPTION_NO_DEFINE_COMMON},
     '\0', NULL, N_("Do not define Common storage"), TWO_DASHES },
   { {"no-demangle", no_argument, NULL, OPTION_NO_DEMANGLE },
@@ -1598,29 +1598,33 @@ parse_args (unsigned argc, char **argv)
   /* Run a couple of checks on the map filename.  */
   if (config.map_filename)
     {
-      /* If name has been provided then use the
-	 output filename with a .map extension.  */
       if (config.map_filename[0] == 0)
 	{
-	  /* FIXME: This is a memory leak as the string is never freed.  */
-	  if (asprintf (&config.map_filename, "%s.map", output_filename) < 0)
-	    einfo (_("%F%P: %s: can not create name of map file: %E\n"));
+	  einfo (_("%P: no file/directory name provided for map output; ignored\n"));
+	  config.map_filename = NULL;
 	}
       else
 	{
 	  struct stat s;
 
 	  /* If the map filename is actually a directory then create
-	     a file inside it, again based upon the output filename.  */
+	     a file inside it, based upon the output filename.  */
 	  if (stat (config.map_filename, &s) >= 0
 	      && S_ISDIR (s.st_mode))
 	    {
 	      char * new_name;
 
-	      /* FIXME: Another memory leak.  */
+	      /* FIXME: This is a (trivial) memory leak.  */
 	      if (asprintf (&new_name, "%s/%s.map",
 			    config.map_filename, output_filename) < 0)
-		einfo (_("%F%P: %s: can not create name of map file: %E\n"));
+		{
+		  /* If this alloc fails then something is probably very
+		     wrong.  Better to halt now rather than continue on
+		     into more problems.  */
+		  einfo (_("%P%F: cannot create name for linker map file: %E\n"));
+		  new_name = NULL;
+		}
+
 	      config.map_filename = new_name;
 	    }
 	}