[RFC] Fix build failure in stap-probe.c.
Sergio Durigan Junior
sergiodj@redhat.com
Wed May 2 18:56:00 GMT 2012
On Wednesday, May 02 2012, Doug Evans wrote:
> Hi.
>
> I'm getting build failures, gcc is complaining that "opcode" and
> "lookahead_opcode" "may be used uninitialized".
Hi Doug,
I'm not seeing this error when I compile (even with -O2), but I believe
you :-).
> cc1: warnings being treated as errors
> ../../src/gdb/stap-probe.c: In function 'stap_parse_argument_1':
> ../../src/gdb/stap-probe.c:1558: error: 'lookahead_opcode' may be used uninitialized in this function
> ../../src/gdb/stap-probe.c:813: note: 'lookahead_opcode' was declared here
> ../../src/gdb/stap-probe.c:1558: error: 'opcode' may be used uninitialized in this function
> ../../src/gdb/stap-probe.c:778: note: 'opcode' was declared here
> make: *** [stap-probe.o] Error 1
>
> This patch is just RFC.
> IIUC the code already watches for valid operators before
> calling stap_get_opcode, so stap_get_opcode should "never" return zero.
> So I'm wondering if maybe step_get_opcode should be changed
> to always succeed and always set the opcode.
You're right. Does this patch work for you?
2012-05-02 Sergio Durigan Junior <sergiodj@redhat.com>
* stap-probe.c (stap_is_operator): Change declaration.
(stap_get_opcode): Change return value.
(stap_parse_argument_1): Update calls to `stap_get_opcode' and
`stap_parse_argument_1'.
---
gdb/stap-probe.c | 101 ++++++++++++++++++++++++++++++++---------------------
1 files changed, 61 insertions(+), 40 deletions(-)
diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
index d1a38da..273ae07 100644
--- a/gdb/stap-probe.c
+++ b/gdb/stap-probe.c
@@ -154,7 +154,7 @@ static void stap_parse_argument_conditionally (struct stap_parse_info *p);
/* Returns 1 if *S is an operator, zero otherwise. */
-static int stap_is_operator (char op);
+static int stap_is_operator (const char *op);
static void
show_stapexpressiondebug (struct ui_file *file, int from_tty,
@@ -209,111 +209,107 @@ stap_get_operator_prec (enum exp_opcode op)
/* Given S, read the operator in it and fills the OP pointer with its code.
Return 1 on success, zero if the operator was not recognized. */
-static int
-stap_get_opcode (const char **s, enum exp_opcode *op)
+static enum exp_opcode
+stap_get_opcode (const char **s)
{
const char c = **s;
- int ret = 1;
+ enum exp_opcode op;
*s += 1;
switch (c)
{
case '*':
- *op = BINOP_MUL;
+ op = BINOP_MUL;
break;
case '/':
- *op = BINOP_DIV;
+ op = BINOP_DIV;
break;
case '%':
- *op = BINOP_REM;
+ op = BINOP_REM;
break;
case '<':
- *op = BINOP_LESS;
+ op = BINOP_LESS;
if (**s == '<')
{
*s += 1;
- *op = BINOP_LSH;
+ op = BINOP_LSH;
}
else if (**s == '=')
{
*s += 1;
- *op = BINOP_LEQ;
+ op = BINOP_LEQ;
}
else if (**s == '>')
{
*s += 1;
- *op = BINOP_NOTEQUAL;
+ op = BINOP_NOTEQUAL;
}
break;
case '>':
- *op = BINOP_GTR;
+ op = BINOP_GTR;
if (**s == '>')
{
*s += 1;
- *op = BINOP_RSH;
+ op = BINOP_RSH;
}
else if (**s == '=')
{
*s += 1;
- *op = BINOP_GEQ;
+ op = BINOP_GEQ;
}
break;
case '|':
- *op = BINOP_BITWISE_IOR;
+ op = BINOP_BITWISE_IOR;
if (**s == '|')
{
*s += 1;
- *op = BINOP_LOGICAL_OR;
+ op = BINOP_LOGICAL_OR;
}
break;
case '&':
- *op = BINOP_BITWISE_AND;
+ op = BINOP_BITWISE_AND;
if (**s == '&')
{
*s += 1;
- *op = BINOP_LOGICAL_AND;
+ op = BINOP_LOGICAL_AND;
}
break;
case '^':
- *op = BINOP_BITWISE_XOR;
+ op = BINOP_BITWISE_XOR;
break;
case '!':
- *op = UNOP_LOGICAL_NOT;
+ op = UNOP_LOGICAL_NOT;
break;
case '+':
- *op = BINOP_ADD;
+ op = BINOP_ADD;
break;
case '-':
- *op = BINOP_SUB;
+ op = BINOP_SUB;
break;
case '=':
- if (**s != '=')
- {
- ret = 0;
- break;
- }
- *op = BINOP_EQUAL;
+ gdb_assert (**s == '=');
+ op = BINOP_EQUAL;
break;
default:
- /* We didn't find any operator. */
- *s -= 1;
- return 0;
+ internal_error (__FILE__, __LINE__,
+ _("Invalid opcode in expression `%s' for SystemTap"
+ "probe"), *s);
}
- return ret;
+ return op;
}
/* Given the bitness of the argument, represented by B, return the
@@ -773,7 +769,7 @@ stap_parse_argument_1 (struct stap_parse_info *p, int has_lhs,
enum exp_opcode opcode;
enum stap_operand_prec cur_prec;
- if (!stap_is_operator (*p->arg))
+ if (!stap_is_operator (p->arg))
error (_("Invalid operator `%c' on expression `%s'."), *p->arg,
p->saved_arg);
@@ -782,7 +778,7 @@ stap_parse_argument_1 (struct stap_parse_info *p, int has_lhs,
operator. If this operator's precedence is lower than PREC, we
should return and not advance the expression buffer pointer. */
tmp_exp_buf = p->arg;
- stap_get_opcode (&tmp_exp_buf, &opcode);
+ opcode = stap_get_opcode (&tmp_exp_buf);
cur_prec = stap_get_operator_prec (opcode);
if (cur_prec < prec)
@@ -803,7 +799,7 @@ stap_parse_argument_1 (struct stap_parse_info *p, int has_lhs,
/* While we still have operators, try to parse another
right-side, but using the current right-side as a left-side. */
- while (*p->arg && stap_is_operator (*p->arg))
+ while (*p->arg && stap_is_operator (p->arg))
{
enum exp_opcode lookahead_opcode;
enum stap_operand_prec lookahead_prec;
@@ -811,7 +807,7 @@ stap_parse_argument_1 (struct stap_parse_info *p, int has_lhs,
/* Saving the current expression buffer position. The explanation
is the same as above. */
tmp_exp_buf = p->arg;
- stap_get_opcode (&tmp_exp_buf, &lookahead_opcode);
+ lookahead_opcode = stap_get_opcode (&tmp_exp_buf);
lookahead_prec = stap_get_operator_prec (lookahead_opcode);
if (lookahead_prec <= prec)
@@ -1013,11 +1009,36 @@ stap_get_probe_argument_count (struct probe *probe_generic,
otherwise. */
static int
-stap_is_operator (char op)
+stap_is_operator (const char *op)
{
- return (op == '+' || op == '-' || op == '*' || op == '/'
- || op == '>' || op == '<' || op == '!' || op == '^'
- || op == '|' || op == '&' || op == '%' || op == '=');
+ int ret = 1;
+
+ switch (*op)
+ {
+ case '*':
+ case '/':
+ case '%':
+ case '^':
+ case '!':
+ case '+':
+ case '-':
+ case '<':
+ case '>':
+ case '|':
+ case '&':
+ break;
+
+ case '=':
+ if (op[1] != '=')
+ ret = 0;
+ break;
+
+ default:
+ /* We didn't find any operator. */
+ ret = 0;
+ }
+
+ return ret;
}
static struct stap_probe_arg *
--
1.7.7.6
--
Sergio
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