shell/math: fix one name check, other minor cleanups

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 12 insertions, 8 deletions

diff --git a/shell/math.c b/shell/math.c
index af8e691fe..57eb56952 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -245,6 +245,9 @@ typedef struct {
         char *var_name;
 } var_or_num_t;
 
+#define VALID_NAME(name) ((name) && (name) != SECOND_VAL_VALID)
+#define NOT_NAME(name) (!(name) || (name) == SECOND_VAL_VALID)
+
 
 typedef struct remembered_name {
         struct remembered_name *next;
@@ -258,7 +261,7 @@ evaluate_string(arith_state_t *math_state, const char *expr);
 static const char*
 arith_lookup_val(arith_state_t *math_state, var_or_num_t *t)
 {
-        if (t->var_name && t->var_name != SECOND_VAL_VALID) {
+        if (VALID_NAME(t->var_name)) {
                 const char *p = math_state->lookupvar(t->var_name);
                 if (p) {
                         remembered_name *cur;
@@ -275,16 +278,15 @@ arith_lookup_val(arith_state_t *math_state, var_or_num_t *t)
                         }
 
                         /* push current var name */
-                        cur = math_state->list_of_recursed_names;
                         remember.var_name = t->var_name;
-                        remember.next = cur;
+                        remember.next = math_state->list_of_recursed_names;
                         math_state->list_of_recursed_names = &remember;
 
                         /* recursively evaluate p as expression */
                         t->val = evaluate_string(math_state, p);
 
                         /* pop current var name */
-                        math_state->list_of_recursed_names = cur;
+                        math_state->list_of_recursed_names = remember.next;
 
                         return math_state->errmsg;
                 }
@@ -446,7 +448,7 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_
         if (is_assign_op(op)) {
                 char buf[sizeof(arith_t)*3 + 2];
 
-                if (!top_of_stack->var_name || top_of_stack->var_name == SECOND_VAL_VALID) {
+                if (NOT_NAME(top_of_stack->var_name)) {
                         /* Hmm, 1=2 ? */
                         goto syntax_err;
                 }
@@ -708,9 +710,11 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                 if ((expr[0] == '+' || expr[0] == '-')
                  && (expr[1] == expr[0])
                 ) {
-                        if (numstackptr == numstack || !numstackptr[-1].var_name) { /* not a VAR++ */
+                        if (numstackptr == numstack || NOT_NAME(numstackptr[-1].var_name)) {
+                                /* not a VAR++ */
                                 char next = skip_whitespace(expr + 2)[0];
-                                if (!(isalpha(next) || next == '_')) { /* not a ++VAR */
+                                if (!(isalpha(next) || next == '_')) {
+                                        /* not a ++VAR */
                                         //bb_error_msg("special %c%c", expr[0], expr[0]);
                                         op = (expr[0] == '+' ? TOK_ADD : TOK_SUB);
                                         expr++;
@@ -802,7 +806,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                                         if (prev_op == TOK_LPAREN) {
 //bb_error_msg("prev_op == TOK_LPAREN");
 //bb_error_msg("  %p %p numstackptr[-1].var_name:'%s'", numstack, numstackptr-1, numstackptr[-1].var_name);
-                                                if (numstackptr[-1].var_name && numstackptr[-1].var_name != SECOND_VAL_VALID) {
+                                                if (VALID_NAME(numstackptr[-1].var_name)) {
                                                         /* Expression is (var), lookup now */
                                                         errmsg = arith_lookup_val(math_state, &numstackptr[-1]);
                                                         if (errmsg)