Support broken gcc test for gas string merge support

On casual reading of older gcc configure scripts it might be supposed
that the test for gas string merge support tries with %progbits after
a fail on ARM with @progbits.  It doesn't succeed due to a bug.  So to
support building of older gcc's for ARM without users having to edit
gcc sources, add a hack to gas.  The hack can disappear in a few years
when building older gcc's likely requires other work too.

I've changed the docs to reflect what we actually allow for .section
syntax prior to this patch.  (No way should this hack be documented as
allowed!)

	PR 32491
	* config/obj-elf.c (obj_elf_section): Allow missing entsize
	for ARM gcc configure bug.
	* doc/as.texi: Correct syntax of ELF .section directive.
	* testsuite/gas/elf/string.s,
	* testsuite/gas/elf/string.d: Test it.

4 files changed, 27 insertions, 7 deletions

diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c
index 6670b9a..b3b2025 100644
--- a/gas/config/obj-elf.c
+++ b/gas/config/obj-elf.c
@@ -1324,13 +1324,27 @@ obj_elf_section (int push)
 		  && (bfd_section_flags (now_seg)
 		      & (SEC_MERGE | SEC_STRINGS)) != 0)
 		goto fetch_entsize;
-	      entsize = get_absolute_expression ();
-	      SKIP_WHITESPACE ();
-	      if (entsize <= 0)
+	      if (is_end_of_line[(unsigned char) *input_line_pointer])
+		{
+		  /* ??? This is here for older versions of gcc that
+		     test for gas string merge support with
+		     '.section .rodata.str, "aMS", @progbits, 1'
+		     Unfortunately '@' begins a comment on arm.
+		     This isn't as_warn because gcc tests with
+		     --fatal-warnings. */
+		  as_tsktsk (_("missing merge / string entity size, 1 assumed"));
+		  entsize = 1;
+		}
+	      else
 		{
-		  as_warn (_("invalid merge / string entity size"));
-		  attr &= ~(SHF_MERGE | SHF_STRINGS);
-		  entsize = 0;
+		  entsize = get_absolute_expression ();
+		  SKIP_WHITESPACE ();
+		  if (entsize <= 0)
+		    {
+		      as_warn (_("invalid merge / string entity size"));
+		      attr &= ~(SHF_MERGE | SHF_STRINGS);
+		      entsize = 0;
+		    }
 		}
 	    }
 	  else if ((attr & (SHF_MERGE | SHF_STRINGS)) != 0 && inherit
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index d95ce9c..afe1737 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -6884,7 +6884,7 @@ This is one of the ELF section stack manipulation directives.  The others are
 For ELF targets, the @code{.section} directive is used like this:
 
 @smallexample
-.section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
+.section @var{name} [, "@var{flags}"[, @@@var{type}][,@var{flag_specific_arguments}]]
 @end smallexample
 
 @anchor{Section Name Substitutions}
diff --git a/gas/testsuite/gas/elf/string.d b/gas/testsuite/gas/elf/string.d
index 6fcfe46..6dbd2d5 100644
--- a/gas/testsuite/gas/elf/string.d
+++ b/gas/testsuite/gas/elf/string.d
@@ -1,9 +1,11 @@
 #readelf: -SW
 #name: string sections
+#warning: (.*missing merge / string entity size, 1 assumed)?
 
 #...
 [ 	]*\[.*\][ 	]+\.str1[ 	]+PROGBITS[ 	]+0+[ 	]+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+01[ 	]+S[ 	]+.*
 [ 	]*\[.*\][ 	]+\.str2[ 	]+PROGBITS[ 	]+0+[ 	]+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+01[ 	]+S[ 	]+.*
 [ 	]*\[.*\][ 	]+\.str3[ 	]+PROGBITS[ 	]+0+[ 	]+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+01[ 	]+S[ 	]+.*
 [ 	]*\[.*\][ 	]+\.str4[ 	]+PROGBITS[ 	]+0+[ 	]+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+02[ 	]+S[ 	]+.*
+[ 	]*\[.*\][ 	]+\.rodata\.str[ 	]+PROGBITS[ 	]+0+[ 	]+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+01[ 	]+AMS[ 	]+.*
 #pass
diff --git a/gas/testsuite/gas/elf/string.s b/gas/testsuite/gas/elf/string.s
index 78c22f7..7733cfb 100644
--- a/gas/testsuite/gas/elf/string.s
+++ b/gas/testsuite/gas/elf/string.s
@@ -8,3 +8,7 @@
 	.asciz "ghi"
 	.section .str4,"S",%progbits,2
 	.short 32, 0
+# The following is used in older versions of gcc to test for gas
+# string merge support.  On arm, @ begins a comment.
+	.section .rodata.str, "aMS", @progbits, 1
+	.asciz "jkl"