shell/math: return string error indicator, not integer

function                                             old     new   delta
expand_and_evaluate_arith                             87     106     +19
expand_one_var                                      1563    1570      +7
arith                                                 12      18      +6
evaluate_string                                      678     680      +2
arith_apply                                         1269    1271      +2
builtin_umask                                        133     132      -1
ash_arith                                            118      75     -43
expand_vars_to_list                                 1094    1038     -56
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/3 up/down: 36/-100)           Total: -64 bytes

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

1 files changed, 40 insertions, 41 deletions

diff --git a/shell/math.c b/shell/math.c
index 839715776..871c06c3e 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -26,26 +26,26 @@
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 /* Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
-
-   Permission is hereby granted, free of charge, to any person obtaining
-   a copy of this software and associated documentation files (the
-   "Software"), to deal in the Software without restriction, including
-   without limitation the rights to use, copy, modify, merge, publish,
-   distribute, sublicense, and/or sell copies of the Software, and to
-   permit persons to whom the Software is furnished to do so, subject to
-   the following conditions:
-
-   The above copyright notice and this permission notice shall be
-   included in all copies or substantial portions of the Software.
-
-   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-*/
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
 
 /* This is my infix parser/evaluator. It is optimized for size, intended
  * as a replacement for yacc-based parsers. However, it may well be faster
@@ -60,9 +60,6 @@
  * this is based (this code differs in that it applies operators immediately
  * to the stack instead of adding them to a queue to end up with an
  * expression).
- *
- * To use the routine, call it with an expression string and error return
- * pointer
  */
 
 /*
@@ -250,7 +247,7 @@ typedef struct remembered_name {
 static arith_t FAST_FUNC
 evaluate_string(arith_state_t *math_state, const char *expr);
 
-static int
+static const char*
 arith_lookup_val(arith_state_t *math_state, v_n_t *t)
 {
         if (t->var) {
@@ -264,8 +261,8 @@ arith_lookup_val(arith_state_t *math_state, v_n_t *t)
                          */
                         for (cur = math_state->list_of_recursed_names; cur; cur = cur->next) {
                                 if (strcmp(cur->var, t->var) == 0) {
-                                        /* Yes. Expression recursion loop detected */
-                                        return -5;
+                                        /* Yes */
+                                        return "expression recursion loop detected";
                                 }
                         }
 
@@ -281,7 +278,7 @@ arith_lookup_val(arith_state_t *math_state, v_n_t *t)
                         /* pop current var name */
                         math_state->list_of_recursed_names = cur;
 
-                        return math_state->errcode;
+                        return math_state->errmsg;
                 }
                 /* treat undefined var as 0 */
                 t->val = 0;
@@ -292,14 +289,14 @@ arith_lookup_val(arith_state_t *math_state, v_n_t *t)
 /* "Applying" a token means performing it on the top elements on the integer
  * stack. For an unary operator it will only change the top element, but a
  * binary operator will pop two arguments and push the result */
-static NOINLINE int
+static NOINLINE const char*
 arith_apply(arith_state_t *math_state, operator op, v_n_t *numstack, v_n_t **numstackptr)
 {
 #define NUMPTR (*numstackptr)
 
         v_n_t *numptr_m1;
         arith_t numptr_val, rez;
-        int err;
+        const char *err;
 
         /* There is no operator that can work without arguments */
         if (NUMPTR == numstack)
@@ -399,13 +396,13 @@ arith_apply(arith_state_t *math_state, operator op, v_n_t *numstack, v_n_t **num
                 } else if (op == TOK_EXPONENT) {
                         arith_t c;
                         if (numptr_val < 0)
-                                return -3;      /* exponent less than 0 */
+                                return "exponent less than 0";
                         c = 1;
                         while (--numptr_val >= 0)
                             c *= rez;
                         rez = c;
-                } else if (numptr_val==0)          /* zero divisor check */
-                        return -2;
+                } else if (numptr_val == 0)
+                        return "divide by zero";
                 else if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
                         rez /= numptr_val;
                 else if (op == TOK_REM || op == TOK_REM_ASSIGN)
@@ -430,9 +427,9 @@ arith_apply(arith_state_t *math_state, operator op, v_n_t *numstack, v_n_t **num
         numptr_m1->val = rez;
         /* erase var name, it is just a number now */
         numptr_m1->var = NULL;
-        return 0;
+        return NULL;
  err:
-        return -1;
+        return "arithmetic syntax error";
 #undef NUMPTR
 }
 
@@ -498,7 +495,7 @@ static arith_t FAST_FUNC
 evaluate_string(arith_state_t *math_state, const char *expr)
 {
         operator lasttok;
-        int errcode;
+        const char *errmsg;
         const char *start_expr = expr = skip_whitespace(expr);
         unsigned expr_len = strlen(expr) + 2;
         /* Stack of integers */
@@ -512,7 +509,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
         operator *stackptr = stack;
 
         *stackptr++ = lasttok = TOK_LPAREN;     /* start off with a left paren */
-        errcode = 0;
+        errmsg = NULL;
 
         while (1) {
                 const char *p;
@@ -548,7 +545,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                         }
                         if (numstack->var) {
                                 /* expression is $((var)) only, lookup now */
-                                errcode = arith_lookup_val(math_state, numstack);
+                                errmsg = arith_lookup_val(math_state, numstack);
                         }
                         goto ret;
                 }
@@ -663,8 +660,8 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                                                 break;
                                         }
                                 }
-                                errcode = arith_apply(math_state, prev_op, numstack, &numstackptr);
-                                if (errcode)
+                                errmsg = arith_apply(math_state, prev_op, numstack, &numstackptr);
+                                if (errmsg)
                                         goto ret;
                         }
                         if (op == TOK_RPAREN) {
@@ -678,15 +675,17 @@ evaluate_string(arith_state_t *math_state, const char *expr)
         } /* while (1) */
 
  err:
-        numstack->val = errcode = -1;
+        numstack->val = -1;
+        errmsg = "arithmetic syntax error";
  ret:
-        math_state->errcode = errcode;
+        math_state->errmsg = errmsg;
         return numstack->val;
 }
 
 arith_t FAST_FUNC
 arith(arith_state_t *math_state, const char *expr)
 {
+        math_state->errmsg = NULL;
         math_state->list_of_recursed_names = NULL;
         return evaluate_string(math_state, expr);
 }