Re: gas -Werror compilation break [Re: [patch ld bfd gas]: Handle linkonce for cfi generated debug_frame and eh_frame data]

[Alan Modra <amodra at gmail dot com>]

On Fri, May 06, 2011 at 06:57:27PM +0100, Dave Korn wrote:
>   Hmm, still getting this:
> 
> > /n/10/davek/binutils/src.clean/gas/dw2gencfi.c: In function 'cfi_finish':
> > /n/10/davek/binutils/src.clean/gas/dw2gencfi.c:1903:17: error: variable 'ccseg' set but not used [-Werror=unused-but-set-variable]
> > cc1: all warnings being treated as errors

Caught out by my habit of compiling with -fno-inline.  These warnings
are a bit of a pain when you want to reduce struct size as I did with
#if SUPPORT_FRAME_LINKONCE.

Let's clean up some of the conditional compilation.  Shame on me for
not doing this properly in the first place.  SET_CUR_SEG in the
!SUPPORT_FRAME_LINKONCE case is a little tricky since you need to
reference the rhs to ensure no warnings about is_now_linkonce_segment
being unused, but don't want gcc to actually call (or emit) the
function.

	* dw2gencfi.c (CUR_SEG, SET_CUR_SEG, HANDLED, SET_HANDLED): Define.
	Use throughout in place of #if SUPPORT_FRAME_LINKONCE.
	(struct fde_entry): Rename cseg to cur_seg.
	(cfi_change_reg_numbers): Remove ATTRIBUTE_UNUSED.
	(get_cfi_seg): Likewise.  Use if (SUPPORT_FRAME_LINKONCE) rather
	that #if SUPPORT_FRAME_LINKONCE.
	(cfi_finish): Likewise.

Index: gas/dw2gencfi.c
===================================================================
RCS file: /cvs/src/src/gas/dw2gencfi.c,v
retrieving revision 1.53
diff -u -p -r1.53 dw2gencfi.c
--- gas/dw2gencfi.c	5 May 2011 13:11:36 -0000	1.53
+++ gas/dw2gencfi.c	7 May 2011 02:30:31 -0000
@@ -83,6 +83,17 @@
 #endif
 
 #if SUPPORT_FRAME_LINKONCE
+#define CUR_SEG(structp) structp->cur_seg
+#define SET_CUR_SEG(structp, seg) structp->cur_seg = seg 
+#define HANDLED(structp) structp->handled
+#define SET_HANDLED(structp, val) structp->handled = val
+#else
+#define CUR_SEG(structp) NULL
+#define SET_CUR_SEG(structp, seg) (void) (0 && seg)
+#define HANDLED(structp) 0
+#define SET_HANDLED(structp, val) (void) (0 && val)
+#endif
+
 /* Private segment collection list.  */
 struct dwcfi_seg_list
 {
@@ -232,7 +243,6 @@ dwcfi_hash_find_or_make (segT cseg, cons
 
   return item;
 }
-#endif
 
 /* ??? Share this with dwarf2cfg.c.  */
 #ifndef TC_DWARF2_EMIT_OFFSET
@@ -302,7 +312,7 @@ struct fde_entry
 {
   struct fde_entry *next;
 #if SUPPORT_FRAME_LINKONCE
-  segT cseg;
+  segT cur_seg;
 #endif
   symbolS *start_address;
   symbolS *end_address;
@@ -371,10 +381,8 @@ alloc_fde_entry (void)
   frchain_now->frch_cfi_data->cur_fde_data = fde;
   *last_fde_data = fde;
   last_fde_data = &fde->next;
-#if SUPPORT_FRAME_LINKONCE
-  fde->cseg = is_now_linkonce_segment ();
-  fde->handled = 0;
-#endif
+  SET_CUR_SEG (fde, is_now_linkonce_segment ());
+  SET_HANDLED (fde, 0);
   fde->last = &fde->data;
   fde->return_column = DWARF2_DEFAULT_RETURN_COLUMN;
   fde->per_encoding = DW_EH_PE_omit;
@@ -398,9 +406,7 @@ alloc_cfi_insn_data (void)
 
   *cur_fde_data->last = insn;
   cur_fde_data->last = &insn->next;
-#if SUPPORT_FRAME_LINKONCE
-  insn->cur_seg = is_now_linkonce_segment ();
-#endif
+  SET_CUR_SEG (insn, is_now_linkonce_segment ());
   return insn;
 }
 
@@ -1569,10 +1575,8 @@ output_cie (struct cie_entry *cie, bfd_b
     {
       for (i = cie->first; i != cie->last; i = i->next)
         {
-#if SUPPORT_FRAME_LINKONCE
-	  if (i->cur_seg != cie->cur_seg)
+	  if (CUR_SEG (i) != CUR_SEG (cie))
 	    continue;
-#endif
 	  output_cfi_insn (i);
 	}
     }
@@ -1682,9 +1686,7 @@ output_fde (struct fde_entry *fde, struc
     }
 
   for (; first; first = first->next)
-#if SUPPORT_FRAME_LINKONCE
-    if (first->cur_seg == fde->cseg)
-#endif
+    if (CUR_SEG (first) == CUR_SEG (fde))
       output_cfi_insn (first);
 
   frag_align (align, DW_CFA_nop, 0);
@@ -1700,10 +1702,8 @@ select_cie_for_fde (struct fde_entry *fd
 
   for (cie = cie_root; cie; cie = cie->next)
     {
-#if SUPPORT_FRAME_LINKONCE
-      if (cie->cur_seg != fde->cseg)
+      if (CUR_SEG (cie) != CUR_SEG (fde))
 	continue;
-#endif
       if (cie->return_column != fde->return_column
 	  || cie->signal_frame != fde->signal_frame
 	  || cie->per_encoding != fde->per_encoding
@@ -1802,9 +1802,7 @@ select_cie_for_fde (struct fde_entry *fd
   cie = (struct cie_entry *) xmalloc (sizeof (struct cie_entry));
   cie->next = cie_root;
   cie_root = cie;
-#if SUPPORT_FRAME_LINKONCE
-  cie->cur_seg = fde->cseg;
-#endif
+  SET_CUR_SEG (cie, CUR_SEG (fde));
   cie->return_column = fde->return_column;
   cie->signal_frame = fde->signal_frame;
   cie->per_encoding = fde->per_encoding;
@@ -1829,14 +1827,12 @@ select_cie_for_fde (struct fde_entry *fd
 
 #ifdef md_reg_eh_frame_to_debug_frame
 static void
-cfi_change_reg_numbers (struct cfi_insn_data *insn, segT ccseg ATTRIBUTE_UNUSED)
+cfi_change_reg_numbers (struct cfi_insn_data *insn, segT ccseg)
 {
   for (; insn; insn = insn->next)
     {
-#if SUPPORT_FRAME_LINKONCE
-      if (insn->cur_seg != ccseg)
+      if (CUR_SEG (insn) != ccseg)
         continue;
-#endif
       switch (insn->insn)
 	{
 	case DW_CFA_advance_loc:
@@ -1878,20 +1874,22 @@ cfi_change_reg_numbers (struct cfi_insn_
 #endif
 
 static segT
-get_cfi_seg (segT cseg ATTRIBUTE_UNUSED,
-	     const char *base, flagword flags, int align)
+get_cfi_seg (segT cseg, const char *base, flagword flags, int align)
 {
-#if SUPPORT_FRAME_LINKONCE
-  struct dwcfi_seg_list *l;
+  if (SUPPORT_FRAME_LINKONCE)
+    {
+      struct dwcfi_seg_list *l;
 
-  l = dwcfi_hash_find_or_make (cseg, base, flags);
+      l = dwcfi_hash_find_or_make (cseg, base, flags);
 
-  cseg = l->seg;
-  subseg_set (cseg, l->subseg);
-#else
-  cseg = subseg_new (base, 0);
-  bfd_set_section_flags (stdoutput, cseg, flags);
-#endif
+      cseg = l->seg;
+      subseg_set (cseg, l->subseg);
+    }
+  else
+    {
+      cseg = subseg_new (base, 0);
+      bfd_set_section_flags (stdoutput, cseg, flags);
+    }
   record_alignment (cseg, align);
   return cseg;
 }
@@ -1914,18 +1912,19 @@ cfi_finish (void)
       save_flag_traditional_format = flag_traditional_format;
       flag_traditional_format = 1;
 
-#if !SUPPORT_FRAME_LINKONCE
-      /* Open .eh_frame section.  */
-      cfi_seg = get_cfi_seg (NULL, ".eh_frame",
-			     SEC_ALLOC | SEC_LOAD | SEC_DATA
-			     | DWARF2_EH_FRAME_READ_ONLY,
-			     EH_FRAME_ALIGNMENT);
+      if (!SUPPORT_FRAME_LINKONCE)
+	{
+	  /* Open .eh_frame section.  */
+	  cfi_seg = get_cfi_seg (NULL, ".eh_frame",
+				 (SEC_ALLOC | SEC_LOAD | SEC_DATA
+				  | DWARF2_EH_FRAME_READ_ONLY),
+				 EH_FRAME_ALIGNMENT);
 #ifdef md_fix_up_eh_frame
-      md_fix_up_eh_frame (cfi_seg);
+	  md_fix_up_eh_frame (cfi_seg);
 #else
-      (void) cfi_seg;
-#endif
+	  (void) cfi_seg;
 #endif
+	}
 
       do
         {
@@ -1941,31 +1940,32 @@ cfi_finish (void)
 
 	  for (fde = all_fde_data; fde ; fde = fde->next)
 	    {
-#if SUPPORT_FRAME_LINKONCE
-	      if (fde->handled != 0)
-	        continue;
-	      if (seek_next_seg && fde->cseg != ccseg)
-	        {
-		  seek_next_seg = 2;
-		  continue;
-		}
-	      if (!seek_next_seg)
-	        {
-		  ccseg = fde->cseg;
-		  /* Open .eh_frame section.  */
-		  cfi_seg = get_cfi_seg (ccseg, ".eh_frame",
-					 SEC_ALLOC | SEC_LOAD | SEC_DATA
-					 | DWARF2_EH_FRAME_READ_ONLY,
-					 EH_FRAME_ALIGNMENT);
+	      if (SUPPORT_FRAME_LINKONCE)
+		{
+		  if (HANDLED (fde))
+		    continue;
+		  if (seek_next_seg && CUR_SEG (fde) != ccseg)
+		    {
+		      seek_next_seg = 2;
+		      continue;
+		    }
+		  if (!seek_next_seg)
+		    {
+		      ccseg = CUR_SEG (fde);
+		      /* Open .eh_frame section.  */
+		      cfi_seg = get_cfi_seg (ccseg, ".eh_frame",
+					     (SEC_ALLOC | SEC_LOAD | SEC_DATA
+					      | DWARF2_EH_FRAME_READ_ONLY),
+					     EH_FRAME_ALIGNMENT);
 #ifdef md_fix_up_eh_frame
-		  md_fix_up_eh_frame (cfi_seg);
+		      md_fix_up_eh_frame (cfi_seg);
 #else
-		  (void) cfi_seg;
+		      (void) cfi_seg;
 #endif
-		  seek_next_seg = 1;
+		      seek_next_seg = 1;
+		    }
+		  SET_HANDLED (fde, 1);
 		}
-	      fde->handled = 1;
-#endif
 
 	      if (fde->end_address == NULL)
 		{
@@ -1980,10 +1980,9 @@ cfi_finish (void)
 	}
       while (SUPPORT_FRAME_LINKONCE && seek_next_seg == 2);
 
-#if SUPPORT_FRAME_LINKONCE
-      for (fde = all_fde_data; fde ; fde = fde->next)
-        fde->handled = 0;
-#endif
+      if (SUPPORT_FRAME_LINKONCE)
+	for (fde = all_fde_data; fde ; fde = fde->next)
+	  SET_HANDLED (fde, 0);
 
       flag_traditional_format = save_flag_traditional_format;
     }
@@ -1992,11 +1991,11 @@ cfi_finish (void)
     {
       int alignment = ffs (DWARF2_ADDR_SIZE (stdoutput)) - 1;
 
-#if !SUPPORT_FRAME_LINKONCE
-      get_cfi_seg (NULL, ".debug_frame",
-		   SEC_READONLY | SEC_DEBUGGING,
-		   alignment);
-#endif
+      if (!SUPPORT_FRAME_LINKONCE)
+	get_cfi_seg (NULL, ".debug_frame",
+		     SEC_READONLY | SEC_DEBUGGING,
+		     alignment);
+
       do
         {
 	  ccseg = NULL;
@@ -2011,25 +2010,26 @@ cfi_finish (void)
 
 	  for (fde = all_fde_data; fde ; fde = fde->next)
 	    {
-#if SUPPORT_FRAME_LINKONCE
-	      if (fde->handled != 0)
-	        continue;
-	      if (seek_next_seg && fde->cseg != ccseg)
-	        {
-		  seek_next_seg = 2;
-		  continue;
-		}
-	      if (!seek_next_seg)
-	        {
-		  ccseg = fde->cseg;
-		  /* Open .debug_frame section.  */
-		  get_cfi_seg (ccseg, ".debug_frame",
-			       SEC_READONLY | SEC_DEBUGGING,
-			       alignment);
-		  seek_next_seg = 1;
+	      if (SUPPORT_FRAME_LINKONCE)
+		{
+		  if (HANDLED (fde))
+		    continue;
+		  if (seek_next_seg && CUR_SEG (fde) != ccseg)
+		    {
+		      seek_next_seg = 2;
+		      continue;
+		    }
+		  if (!seek_next_seg)
+		    {
+		      ccseg = CUR_SEG (fde);
+		      /* Open .debug_frame section.  */
+		      get_cfi_seg (ccseg, ".debug_frame",
+				   SEC_READONLY | SEC_DEBUGGING,
+				   alignment);
+		      seek_next_seg = 1;
+		    }
+		  SET_HANDLED (fde, 1);
 		}
-	      fde->handled = 1;
-#endif
 	      if (fde->end_address == NULL)
 		{
 		  as_bad (_("open CFI at the end of file; missing .cfi_endproc directive"));
@@ -2045,10 +2045,9 @@ cfi_finish (void)
 	}
       while (SUPPORT_FRAME_LINKONCE && seek_next_seg == 2);
 
-#if SUPPORT_FRAME_LINKONCE
-      for (fde = all_fde_data; fde ; fde = fde->next)
-        fde->handled = 0;
-#endif
+      if (SUPPORT_FRAME_LINKONCE)
+	for (fde = all_fde_data; fde ; fde = fde->next)
+	  SET_HANDLED (fde, 0);
     }
 }
 
-- 
Alan Modra
Australia Development Lab, IBM