shell/math: eliminate some redundant stores on return code path

function old new delta evaluate_string 1432 1412 -20 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
author: Denys Vlasenko <vda.linux@googlemail.com> 2023-06-17 19:20:31 +0200
committer: Denys Vlasenko <vda.linux@googlemail.com> 2023-06-17 19:21:28 +0200
commit: 822590f5e29c613dd1401ba4309c0684426fc4f4 (patch)
tree: 339a5e104e751aebd392b44cd7a59fa5dada2556
parent: 19a74a54ded98b28c672d38b79ea9f313f2d89db (diff)
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1 files changed, 23 insertions, 20 deletions
diff --git a/shell/math.c b/shell/math.c
index 3e339a5ec..4b56d1397 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -303,21 +303,21 @@ arith_lookup_val(arith_state_t *math_state, var_or_num_t *t)
 static NOINLINE const char*
 arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_or_num_t **numstackptr)
 {
-#define NUMPTR (*numstackptr)
+#define NUMSTACKPTR (*numstackptr)
        var_or_num_t *top_of_stack;
        arith_t rez;
        /* There is no operator that can work without arguments */
-        if (NUMPTR == numstack)
+        if (NUMSTACKPTR == numstack)
                goto syntax_err;
-        top_of_stack = NUMPTR - 1;
+        top_of_stack = NUMSTACKPTR - 1;
        if (op == TOK_CONDITIONAL_SEP) {
                /* "expr1 ? expr2 : expr3" operation */
                var_or_num_t *expr1 = &top_of_stack[-2];
-                NUMPTR = expr1 + 1;
+                NUMSTACKPTR = expr1 + 1;
                if (expr1 < numstack) /* Example: $((2:3)) */
                        return "malformed ?: operator";
                if (expr1->val != 0) /* select expr2 or expr3 */
@@ -348,12 +348,17 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_
                        goto syntax_err; /* no */
                /* Pop numstack */
-                NUMPTR = top_of_stack; /* this decrements NUMPTR */
+                NUMSTACKPTR = top_of_stack; /* this decrements NUMSTACKPTR */
                top_of_stack--; /* now points to left side */
                if (math_state->evaluation_disabled) {
                        dbg("binary op %02x skipped", op);
                        goto ret_NULL;
+                        /* bash 5.2.12 does not execute "2/0" in disabled
+                         * branches of ?: (and thus does not complain),
+                         * but complains about negative exp: "2**-1".
+                         * I don't think we need to emulate that.
+                         */
                }
                right_side_val = rez;
@@ -457,7 +462,7 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_
        return NULL;
 syntax_err:
        return "arithmetic syntax error";
-#undef NUMPTR
+#undef NUMSTACKPTR
 }
 /* longest must be first */
@@ -630,8 +635,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                if (*expr == '\0') {
                        if (expr == start_expr) {
                                /* Null expression */
-                                numstack->val = 0;
+                                return 0;
-                                goto ret;
                        }
                        /* This is only reached after all tokens have been extracted from the
@@ -650,9 +654,9 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                        /* At this point, we're done with the expression */
                        if (numstackptr != numstack + 1) {
                                /* if there is not exactly one result, it's bad */
-                                goto err;
+                                goto syntax_err;
                        }
-                        goto ret;
+                        return numstack->val;
                }
                p = endofname(expr);
@@ -697,7 +701,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                         * a new number or name. Example: 09v09v09v09v09v09v09v09v09v
                         */
                        if (isalnum(*expr) || *expr == '_')
-                                goto err;
+                                goto syntax_err;
                        if (errno)
                                numstackptr->val = 0; /* bash compat */
                        goto push_num;
@@ -750,7 +754,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                        if (*p == '\0') {
                                /* No next element, operator not found */
                                //math_state->syntax_error_at = expr;
-                                goto err;
+                                goto syntax_err;
                        }
                }
                /* NB: expr now points past the operator */
@@ -812,7 +816,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                        /* binary, ternary or RPAREN */
                        if (lasttok != TOK_NUM) {
                                /* must be preceded by a num */
-                                goto err;
+                                goto syntax_err;
                        }
                        /* if op is RPAREN:
                         *     while opstack is not empty:
@@ -883,7 +887,7 @@ dbg("    numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[
                        } /* while (opstack not empty) */
                        if (op == TOK_RPAREN) /* unpaired RPAREN? */
-                                goto err;
+                                goto syntax_err;
 check_cond:
                        if (op == TOK_CONDITIONAL) {
                                /* We just now evaluated EXPR before "?".
@@ -914,20 +918,19 @@ dbg("    numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[
                                } else if (ternary_level == math_state->evaluation_disabled) {
                                        math_state->evaluation_disabled = 0;
                                        dbg("':' entered: evaluation_disabled=CLEAR");
-                                } /* else: ternary_level > nonzero evaluation_disabled: we are in nested ?:, in its disabled branch */
+                                } /* else: ternary_level > evaluation_disabled && evaluation_disabled != 0 */
-                                        /* do nothing */
+                                        /* We are in nested "?:" while in outer "?:" disabled branch */
+                                        /* do_nothing */
                        }
                        goto tok_found1;
                }
        } /* while (1) */
- err:
+ syntax_err:
        errmsg = "arithmetic syntax error";
 err_with_custom_msg:
-        numstack->val = -1;
- ret:
        math_state->errmsg = errmsg;
-        return numstack->val;
+        return -1;
 }
 arith_t FAST_FUNC
author	Denys Vlasenko <vda.linux@googlemail.com>	2023-06-17 19:20:31 +0200
committer	Denys Vlasenko <vda.linux@googlemail.com>	2023-06-17 19:21:28 +0200
commit	822590f5e29c613dd1401ba4309c0684426fc4f4 (patch)
tree	339a5e104e751aebd392b44cd7a59fa5dada2556
parent	19a74a54ded98b28c672d38b79ea9f313f2d89db (diff)
download	busybox-w32-822590f5e29c613dd1401ba4309c0684426fc4f4.tar.gz busybox-w32-822590f5e29c613dd1401ba4309c0684426fc4f4.tar.bz2 busybox-w32-822590f5e29c613dd1401ba4309c0684426fc4f4.zip