Remove magic numbers in m68k-dis.c:print_insn_arg

When I inspect the return values of disassmblers, I happen to see
various -1/-2/-3 magic numbers are used in m68k-dis.c.  This patch
is to replace them with enum.

-1 and -2 is "clearly documented" in print_ins_arg's comments, but
-3 isn't.  In fact, -3 is returned when FETCH_DATA returns false,
which means memory error (because fetch_data return 0 on memory
error).  So I name enum PRINT_INSN_ARG_MEMORY_ERROR for -3.

This patch is a refactor patch, doesn't affect any functionality.

opcodes:

2017-01-13  Yao Qi  <yao.qi@linaro.org>

	* m68k-dis.c (enum print_insn_arg_error): New.
	(NEXTBYTE): Replace -3 with
	PRINT_INSN_ARG_MEMORY_ERROR.
	(NEXTULONG): Likewise.
	(NEXTSINGLE): Likewise.
	(NEXTDOUBLE): Likewise.
	(NEXTDOUBLE): Likewise.
	(NEXTPACKED): Likewise.
	(FETCH_ARG): Likewise.
	(FETCH_DATA): Update comments.
	(print_insn_arg): Update comments. Replace magic numbers with
	enum.
	(match_insn_m68k): Likewise.

2 files changed, 72 insertions, 41 deletions

diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 000948e..0adbdf1 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,19 @@
+2017-01-13  Yao Qi  <yao.qi@linaro.org>
+
+	* m68k-dis.c (enum print_insn_arg_error): New.
+	(NEXTBYTE): Replace -3 with
+	PRINT_INSN_ARG_MEMORY_ERROR.
+	(NEXTULONG): Likewise.
+	(NEXTSINGLE): Likewise.
+	(NEXTDOUBLE): Likewise.
+	(NEXTDOUBLE): Likewise.
+	(NEXTPACKED): Likewise.
+	(FETCH_ARG): Likewise.
+	(FETCH_DATA): Update comments.
+	(print_insn_arg): Update comments. Replace magic numbers with
+	enum.
+	(match_insn_m68k): Likewise.
+
 2017-01-12  Igor Tsimbalist  <igor.v.tsimbalist@intel.com>
 
 	* i386-dis.c (enum): Add PREFIX_EVEX_0F3855, EVEX_W_0F3855_P_2.
diff --git a/opcodes/m68k-dis.c b/opcodes/m68k-dis.c
index de88f23..a14db9a 100644
--- a/opcodes/m68k-dis.c
+++ b/opcodes/m68k-dis.c
@@ -57,13 +57,27 @@ static char *const reg_half_names[] =
 #define COERCE_SIGNED_CHAR(ch) ((int) (((ch) ^ 0x80) & 0xFF) - 128)
 #endif
 
+/* Error code of print_insn_arg's return value.  */
+
+enum print_insn_arg_error
+  {
+    /* An invalid operand is found.  */
+    PRINT_INSN_ARG_INVALID_OPERAND = -1,
+
+    /* An opcode table error.  */
+    PRINT_INSN_ARG_INVALID_OP_TABLE = -2,
+
+    /* A memory error.  */
+    PRINT_INSN_ARG_MEMORY_ERROR = -3,
+  };
+
 /* Get a 1 byte signed integer.  */
 #define NEXTBYTE(p, val)			\
   do						\
     {						\
       p += 2;					\
       if (!FETCH_DATA (info, p))		\
-	return -3;				\
+	return PRINT_INSN_ARG_MEMORY_ERROR;	\
       val = COERCE_SIGNED_CHAR (p[-1]);		\
     }						\
   while (0)
@@ -100,7 +114,7 @@ static char *const reg_half_names[] =
     {									\
       p += 4;								\
       if (!FETCH_DATA (info, p))					\
-	return -3;							\
+	return PRINT_INSN_ARG_MEMORY_ERROR;				\
       val = (unsigned int) ((((((p[-4] << 8) + p[-3]) << 8) + p[-2]) << 8) + p[-1]); \
     }									\
   while (0)
@@ -111,7 +125,7 @@ static char *const reg_half_names[] =
     {								\
       p += 4;							\
       if (!FETCH_DATA (info, p))				\
-	return -3;						\
+	return PRINT_INSN_ARG_MEMORY_ERROR;			\
       floatformat_to_double (& floatformat_ieee_single_big,	\
 			     (char *) p - 4, & val);		\
     }								\
@@ -123,7 +137,7 @@ static char *const reg_half_names[] =
     {								\
       p += 8;							\
       if (!FETCH_DATA (info, p))				\
-	return -3;						\
+	return PRINT_INSN_ARG_MEMORY_ERROR;			\
       floatformat_to_double (& floatformat_ieee_double_big,	\
 			     (char *) p - 8, & val);		\
     }								\
@@ -135,7 +149,7 @@ static char *const reg_half_names[] =
     {							\
       p += 12;						\
       if (!FETCH_DATA (info, p))			\
-	return -3;					\
+	return PRINT_INSN_ARG_MEMORY_ERROR;		\
       floatformat_to_double (& floatformat_m68881_ext,	\
 			     (char *) p - 12, & val);	\
     }							\
@@ -150,7 +164,7 @@ static char *const reg_half_names[] =
     {						\
       p += 12;					\
       if (!FETCH_DATA (info, p))		\
-	return -3;				\
+	return PRINT_INSN_ARG_MEMORY_ERROR;	\
       val = 0.0;				\
     }						\
   while (0)
@@ -168,7 +182,8 @@ struct private
 };
 
 /* Make sure that bytes from INFO->PRIVATE_DATA->BUFFER (inclusive)
-   to ADDR (exclusive) are valid.  Returns 1 for success, 0 on error.  */
+   to ADDR (exclusive) are valid.  Returns 1 for success, 0 on memory
+   error.  */
 #define FETCH_DATA(info, addr) \
   ((addr) <= ((struct private *) (info->private_data))->max_fetched \
    ? 1 : fetch_data ((info), (addr)))
@@ -617,14 +632,13 @@ print_indexed (int basereg,
     {							\
       val = fetch_arg (buffer, place, size, info);	\
       if (val < 0)					\
-	return -3;					\
+	return PRINT_INSN_ARG_MEMORY_ERROR;		\
     }							\
   while (0)
 
 /* Returns number of bytes "eaten" by the operand, or
-   return -1 if an invalid operand was found, or -2 if
-   an opcode tabe error was found or -3 to simply abort.
-   ADDR is the pc for this arg to be relative to.  */
+   return enum print_insn_arg_error.  ADDR is the pc for this arg to be
+   relative to.  */
 
 static int
 print_insn_arg (const char *d,
@@ -864,7 +878,7 @@ print_insn_arg (const char *d,
 	  (*info->fprintf_func) (info->stream, "{#%d}", val);
 	}
       else
-	return -1;
+	return PRINT_INSN_ARG_INVALID_OPERAND;
       break;
 
     case '#':
@@ -881,11 +895,11 @@ print_insn_arg (const char *d,
       else if (place == 'b')
 	NEXTBYTE (p1, val);
       else if (place == 'w' || place == 'W')
-	NEXTWORD (p1, val, -3);
+	NEXTWORD (p1, val, PRINT_INSN_ARG_MEMORY_ERROR);
       else if (place == 'l')
-	NEXTLONG (p1, val, -3);
+	NEXTLONG (p1, val, PRINT_INSN_ARG_MEMORY_ERROR);
       else
-	return -2;
+	return PRINT_INSN_ARG_INVALID_OP_TABLE;
 
       (*info->fprintf_func) (info->stream, "#%d", val);
       break;
@@ -896,26 +910,26 @@ print_insn_arg (const char *d,
       else if (place == 'B')
 	disp = COERCE_SIGNED_CHAR (buffer[1]);
       else if (place == 'w' || place == 'W')
-	NEXTWORD (p, disp, -3);
+	NEXTWORD (p, disp, PRINT_INSN_ARG_MEMORY_ERROR);
       else if (place == 'l' || place == 'L' || place == 'C')
-	NEXTLONG (p, disp, -3);
+	NEXTLONG (p, disp, PRINT_INSN_ARG_MEMORY_ERROR);
       else if (place == 'g')
 	{
 	  NEXTBYTE (buffer, disp);
 	  if (disp == 0)
-	    NEXTWORD (p, disp, -3);
+	    NEXTWORD (p, disp, PRINT_INSN_ARG_MEMORY_ERROR);
 	  else if (disp == -1)
-	    NEXTLONG (p, disp, -3);
+	    NEXTLONG (p, disp, PRINT_INSN_ARG_MEMORY_ERROR);
 	}
       else if (place == 'c')
 	{
 	  if (buffer[1] & 0x40)		/* If bit six is one, long offset.  */
-	    NEXTLONG (p, disp, -3);
+	    NEXTLONG (p, disp, PRINT_INSN_ARG_MEMORY_ERROR);
 	  else
-	    NEXTWORD (p, disp, -3);
+	    NEXTWORD (p, disp, PRINT_INSN_ARG_MEMORY_ERROR);
 	}
       else
-	return -2;
+	return PRINT_INSN_ARG_INVALID_OP_TABLE;
 
       (*info->print_address_func) (addr + disp, info);
       break;
@@ -924,7 +938,7 @@ print_insn_arg (const char *d,
       {
 	int val1;
 
-	NEXTWORD (p, val, -3);
+	NEXTWORD (p, val, PRINT_INSN_ARG_MEMORY_ERROR);
 	FETCH_ARG (3, val1);
 	(*info->fprintf_func) (info->stream, "%s@(%d)", reg_names[val1 + 8], val);
 	break;
@@ -952,14 +966,14 @@ print_insn_arg (const char *d,
       else if (val == 3)
 	(*info->fprintf_func) (info->stream, ">>");
       else
-	return -1;
+	return PRINT_INSN_ARG_INVALID_OPERAND;
       break;
 
     case 'I':
       /* Get coprocessor ID... */
       val = fetch_arg (buffer, 'd', 3, info);
       if (val < 0)
-	return -3;
+	return PRINT_INSN_ARG_MEMORY_ERROR;
       if (val != 1)				/* Unusual coprocessor ID?  */
 	(*info->fprintf_func) (info->stream, "(cpid=%d) ", val);
       break;
@@ -992,19 +1006,19 @@ print_insn_arg (const char *d,
 	{
 	  val = fetch_arg (buffer, 'x', 6, info);
 	  if (val < 0)
-	    return -3;
+	    return PRINT_INSN_ARG_MEMORY_ERROR;
 	  val = ((val & 7) << 3) + ((val >> 3) & 7);
 	}
       else
 	{
 	  val = fetch_arg (buffer, 's', 6, info);
 	  if (val < 0)
-	    return -3;
+	    return PRINT_INSN_ARG_MEMORY_ERROR;
 	}
 
       /* If the <ea> is invalid for *d, then reject this match.  */
       if (!m68k_valid_ea (*d, val))
-	return -1;
+	return PRINT_INSN_ARG_INVALID_OPERAND;
 
       /* Get register number assuming address register.  */
       regno = (val & 7) + 8;
@@ -1032,21 +1046,21 @@ print_insn_arg (const char *d,
 	  break;
 
 	case 5:
-	  NEXTWORD (p, val, -3);
+	  NEXTWORD (p, val, PRINT_INSN_ARG_MEMORY_ERROR);
 	  (*info->fprintf_func) (info->stream, "%s@(%d)", regname, val);
 	  break;
 
 	case 6:
 	  p = print_indexed (regno, p, addr, info);
 	  if (p == NULL)
-	    return -3;
+	    return PRINT_INSN_ARG_MEMORY_ERROR;
 	  break;
 
 	case 7:
 	  switch (val & 7)
 	    {
 	    case 0:
-	      NEXTWORD (p, val, -3);
+	      NEXTWORD (p, val, PRINT_INSN_ARG_MEMORY_ERROR);
 	      (*info->print_address_func) (val, info);
 	      break;
 
@@ -1056,7 +1070,7 @@ print_insn_arg (const char *d,
 	      break;
 
 	    case 2:
-	      NEXTWORD (p, val, -3);
+	      NEXTWORD (p, val, PRINT_INSN_ARG_MEMORY_ERROR);
 	      (*info->fprintf_func) (info->stream, "%%pc@(");
 	      (*info->print_address_func) (addr + val, info);
 	      (*info->fprintf_func) (info->stream, ")");
@@ -1065,7 +1079,7 @@ print_insn_arg (const char *d,
 	    case 3:
 	      p = print_indexed (-1, p, addr, info);
 	      if (p == NULL)
-		return -3;
+		return PRINT_INSN_ARG_MEMORY_ERROR;
 	      break;
 
 	    case 4:
@@ -1078,12 +1092,12 @@ print_insn_arg (const char *d,
 		  break;
 
 		case 'w':
-		  NEXTWORD (p, val, -3);
+		  NEXTWORD (p, val, PRINT_INSN_ARG_MEMORY_ERROR);
 		  flt_p = 0;
 		  break;
 
 		case 'l':
-		  NEXTLONG (p, val, -3);
+		  NEXTLONG (p, val, PRINT_INSN_ARG_MEMORY_ERROR);
 		  flt_p = 0;
 		  break;
 
@@ -1104,7 +1118,7 @@ print_insn_arg (const char *d,
 		  break;
 
 		default:
-		  return -1;
+		  return PRINT_INSN_ARG_INVALID_OPERAND;
 	      }
 	      if (flt_p)	/* Print a float? */
 		(*info->fprintf_func) (info->stream, "#0e%g", flval);
@@ -1113,7 +1127,7 @@ print_insn_arg (const char *d,
 	      break;
 
 	    default:
-	      return -1;
+	      return PRINT_INSN_ARG_INVALID_OPERAND;
 	    }
 	}
 
@@ -1134,7 +1148,7 @@ print_insn_arg (const char *d,
 	  {
 	    char doneany;
 	    p1 = buffer + 2;
-	    NEXTWORD (p1, val, -3);
+	    NEXTWORD (p1, val, PRINT_INSN_ARG_MEMORY_ERROR);
 	    /* Move the pointer ahead if this point is farther ahead
 	       than the last.  */
 	    p = p1 > p ? p1 : p;
@@ -1215,7 +1229,7 @@ print_insn_arg (const char *d,
 	    (*info->fprintf_func) (info->stream, "%s", fpcr_names[val]);
 	  }
 	else
-	  return -2;
+	  return PRINT_INSN_ARG_INVALID_OP_TABLE;
       break;
 
     case 'X':
@@ -1310,7 +1324,7 @@ print_insn_arg (const char *d,
       break;
 
     default:
-      return -2;
+      return PRINT_INSN_ARG_INVALID_OP_TABLE;
     }
 
   return p - p0;
@@ -1420,7 +1434,8 @@ match_insn_m68k (bfd_vma memaddr,
 
       if (eaten >= 0)
 	p += eaten;
-      else if (eaten == -1 || eaten == -3)
+      else if (eaten == PRINT_INSN_ARG_INVALID_OPERAND
+	       || eaten == PRINT_INSN_ARG_MEMORY_ERROR)
 	{
 	  info->fprintf_func = save_printer;
 	  info->print_address_func = save_print_address;