[PATCH 5/8] Remove magic numbers in m68k-dis.c:print_insn_arg

Yao Qi
2017-01-10T12:26:42Z

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:

2017-01-10 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_DATA): Update comments.
(print_insn_arg): Update comments. Replace magic numbers with
enum.
(match_insn_m68k): Likewise.
---
opcodes/m68k-dis.c | 95 +++++++++++++++++++++++++++++++-----------------------
1 file changed, 55 insertions(+), 40 deletions(-)

diff --git a/opcodes/m68k-dis.c b/opcodes/m68k-dis.c
index de88f23..3159a47 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)))
@@ -622,9 +637,8 @@ print_indexed (int basereg,
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;
--
1.9.1