gas: improve C_BSTAT and C_STSYM symbols handling on XCOFF

A C_BSTAT debug symbol specifies the beginning of a static block.
Its n_value is the index of the csect containing static symbols.
A C_STSYM debug symbol represents the stabstring of a statically
allocated symbol. Its n_value is the offset in the csect pointed
by the containing C_BSTAT.

These two special n_value were not correctly handled both when
generating object files with gas or when reading them with objdump.
This patch tries to improve that and, above all, to allow gas-generated
object files with such symbols to be accepted by AIX ld.

bfd/
	* coff-bfd.c (bfd_coff_get_syment): Adjust n_value of symbols
	having fix_value = 1 in order to be an index and not a memory
	offset.
	* coffgen.c (coff_get_symbol_info): Likewize.
	(coff_print_symbol): Likewize.

gas/
	* config/tc-ppc.c (ppc_frob_label): Don't change within if
	already set.
	(ppc_stabx): Remove workaround changing exp.X_add_symbol's
	within.
	* config/tc-ppc.h (struct ppc_tc_sy): Update comments.
	* symbols.c (resolve_symbol_value): Remove symbol update
	when final_val is 0 and it's an AIX debug symbol.
	* testsuite/gas/ppc/aix.exp: Add new tests.
	* testsuite/gas/ppc/xcoff-stsym-32.d: New test.
	* testsuite/gas/ppc/xcoff-stsym-64.d: New test.
	* testsuite/gas/ppc/xcoff-stsym.s: New test.

7 files changed, 81 insertions, 3 deletions

diff --git a/gas/config/tc-ppc.c b/gas/config/tc-ppc.c
index 6eeb98c..8c3b0a8 100644
--- a/gas/config/tc-ppc.c
+++ b/gas/config/tc-ppc.c
@@ -2901,8 +2901,13 @@ ppc_frob_label (symbolS *sym)
       symbol_remove (sym, &symbol_rootP, &symbol_lastP);
       symbol_append (sym, symbol_get_tc (ppc_current_csect)->within,
 		     &symbol_rootP, &symbol_lastP);
+      /* Update last csect symbol.  */
       symbol_get_tc (ppc_current_csect)->within = sym;
-      symbol_get_tc (sym)->within = ppc_current_csect;
+
+      /* Some labels like .bs are using within differently.
+         So avoid changing it, if it's already set.  */
+      if (symbol_get_tc (sym)->within == NULL)
+	symbol_get_tc (sym)->within = ppc_current_csect;
     }
 #endif
 
@@ -5056,7 +5061,6 @@ ppc_stabx (int ignore ATTRIBUTE_UNUSED)
             as_bad (_(".stabx of storage class stsym must be within .bs/.es"));
 
           symbol_get_tc (sym)->within = ppc_current_block;
-          symbol_get_tc (exp.X_add_symbol)->within = ppc_current_block;
         }
     }
 
diff --git a/gas/config/tc-ppc.h b/gas/config/tc-ppc.h
index 4e175b0..fb18730 100644
--- a/gas/config/tc-ppc.h
+++ b/gas/config/tc-ppc.h
@@ -130,6 +130,7 @@ struct ppc_tc_sy
   /* For a csect symbol, the last symbol which has been defined in
      this csect, or NULL if none have been defined so far.
      For a .bs symbol, the referenced csect symbol.
+     For a C_STSYM symbol, the containing block (.bs symbol).
      For a label, the enclosing csect.  */
   symbolS *within;
   union
diff --git a/gas/symbols.c b/gas/symbols.c
index 1221680..302eb4b 100644
--- a/gas/symbols.c
+++ b/gas/symbols.c
@@ -1380,7 +1380,17 @@ resolve_symbol_value (symbolS *symp)
 	      && add_symbol->flags.resolving)
 	    break;
 
-	  if (finalize_syms && final_val == 0)
+	  if (finalize_syms && final_val == 0
+#ifdef OBJ_XCOFF
+	      /* Avoid changing symp's "within" when dealing with
+		 AIX debug symbols. For some storage classes, "within"
+	         have a special meaning.
+		 C_DWARF should behave like on Linux, thus this check
+		 isn't done to be closer.  */
+	      && ((symbol_get_bfdsym (symp)->flags & BSF_DEBUGGING) == 0
+		  || (S_GET_STORAGE_CLASS (symp) == C_DWARF))
+#endif
+	      )
 	    {
 	      if (add_symbol->flags.local_symbol)
 		add_symbol = local_symbol_convert (add_symbol);
diff --git a/gas/testsuite/gas/ppc/aix.exp b/gas/testsuite/gas/ppc/aix.exp
index 38b7819..aef295b 100644
--- a/gas/testsuite/gas/ppc/aix.exp
+++ b/gas/testsuite/gas/ppc/aix.exp
@@ -81,4 +81,7 @@ if { [istarget "powerpc*-*-aix*"] || [istarget "rs6000-*-aix*"] } then {
 
     run_dump_test "xcoff-tlsm-32"
     run_dump_test "xcoff-tlsm-64"
+
+    run_dump_test "xcoff-stsym-32"
+    run_dump_test "xcoff-stsym-64"
 }
diff --git a/gas/testsuite/gas/ppc/xcoff-stsym-32.d b/gas/testsuite/gas/ppc/xcoff-stsym-32.d
new file mode 100644
index 0000000..501a1dc
--- /dev/null
+++ b/gas/testsuite/gas/ppc/xcoff-stsym-32.d
@@ -0,0 +1,22 @@
+#as: -a32
+#source: xcoff-stsym.s
+#objdump: -t
+#name: XCOFF C_STSYM test (32-bit)
+
+.*
+
+SYMBOL TABLE:
+.*
+.*
+.*
+.*
+\[  4\]\(sec  1\).*\(scl 143\) \(nx 0\) 0x0000000a .bs
+\[  5\]\(sec -2\).*\(scl 133\) \(nx 0\) 0x00000000 x:V6
+\[  6\]\(sec  1\).*\(scl 144\) \(nx 0\) 0x00000000 .es
+\[  7\]\(sec  1\).*\(scl 143\) \(nx 0\) 0x0000000a .bs
+\[  8\]\(sec -2\).*\(scl 133\) \(nx 0\) 0x00000004 y:V6
+\[  9\]\(sec  1\).*\(scl 144\) \(nx 0\) 0x00000000 .es
+\[ 10\].* _main\.rw_
+.*
+
+
diff --git a/gas/testsuite/gas/ppc/xcoff-stsym-64.d b/gas/testsuite/gas/ppc/xcoff-stsym-64.d
new file mode 100644
index 0000000..8da109b
--- /dev/null
+++ b/gas/testsuite/gas/ppc/xcoff-stsym-64.d
@@ -0,0 +1,22 @@
+#as: -a64
+#source: xcoff-stsym.s
+#objdump: -t
+#name: XCOFF C_STSYM test (64-bit)
+
+.*
+
+SYMBOL TABLE:
+.*
+.*
+.*
+.*
+\[  4\]\(sec  1\).*\(scl 143\) \(nx 0\) 0x000000000000000a .bs
+\[  5\]\(sec -2\).*\(scl 133\) \(nx 0\) 0x0000000000000000 x:V6
+\[  6\]\(sec  1\).*\(scl 144\) \(nx 0\) 0x0000000000000000 .es
+\[  7\]\(sec  1\).*\(scl 143\) \(nx 0\) 0x000000000000000a .bs
+\[  8\]\(sec -2\).*\(scl 133\) \(nx 0\) 0x0000000000000004 y:V6
+\[  9\]\(sec  1\).*\(scl 144\) \(nx 0\) 0x0000000000000000 .es
+\[ 10\].* _main\.rw_
+.*
+
+
diff --git a/gas/testsuite/gas/ppc/xcoff-stsym.s b/gas/testsuite/gas/ppc/xcoff-stsym.s
new file mode 100644
index 0000000..ae98a81
--- /dev/null
+++ b/gas/testsuite/gas/ppc/xcoff-stsym.s
@@ -0,0 +1,16 @@
+	.file	"main.c"
+	.csect _main.rw_[RW],4
+
+	.csect .text[PR]
+	.bs	_main.rw_[RW]
+	.stabx	"x:V6",x.2,133,0
+	.es
+	.bs	_main.rw_[RW]
+	.stabx	"y:V6",y.1,133,0
+	.es
+
+	.csect _main.rw_[RW],4
+x.2:
+	.long	100
+y.1:
+	.long	110