182e5a4d0
Denys Vlasenko
2023-06-18
Subject
shell/math: decrease stack usage
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shell/math.c+27 -35
| @@ -579,48 +579,40 @@ static arith_t strto_arith_t(const char *nptr, char **endptr) | |
| # endif | |
| #endif | |
| - | //TODO: much better estimation than expr_len/2? Such as: |
| - | //static unsigned estimate_nums_and_names(const char *expr) |
| - | //{ |
| - | // unsigned count = 0; |
| - | // while (*(expr = skip_whitespace(expr)) != '\0') { |
| - | // const char *p; |
| - | // if (isdigit(*expr)) { |
| - | // while (isdigit(*++expr)) |
| - | // continue; |
| - | // count++; |
| - | // continue; |
| - | // } |
| - | // p = endofname(expr); |
| - | // if (p != expr) { |
| - | // expr = p; |
| - | // count++; |
| - | // continue; |
| - | // } |
| - | // } |
| - | // return count; |
| - | //} |
| - | |
| static arith_t | |
| evaluate_string(arith_state_t *math_state, const char *expr) | |
| { | |
| - | operator lasttok; |
| - | const char *errmsg = NULL; |
| - | const char *start_expr = expr = skip_whitespace(expr); |
| - | unsigned expr_len = strlen(expr) + 2; |
| /* Stack of integers/names */ | |
| - | /* There can be no more than strlen(startbuf)/2+1 |
| - | * integers/names in any given correct or incorrect expression. |
| - | * (modulo "09v09v09v09v09v" case, |
| - | * but we have code to detect that early) |
| - | */ |
| - | var_or_num_t *const numstack = alloca((expr_len / 2) * sizeof(numstack[0])); |
| - | var_or_num_t *numstackptr = numstack; |
| + | var_or_num_t *numstack, *numstackptr; |
| /* Stack of operator tokens */ | |
| - | operator *const opstack = alloca(expr_len * sizeof(opstack[0])); |
| - | operator *opstackptr = opstack; |
| + | operator *opstack, *opstackptr; |
| + | operator lasttok; |
| operator insert_op = 0xff; | |
| unsigned ternary_level = 0; | |
| + | const char *errmsg; |
| + | const char *start_expr = expr = skip_whitespace(expr); |
| + | |
| + | { |
| + | unsigned expr_len = strlen(expr) + 2; |
| + | /* If LOTS of whitespace, do not blow up the estimation */ |
| + | const char *p = expr; |
| + | while (*p) { |
| + | /* in a run of whitespace, count only 1st char */ |
| + | if (isspace(*p)) { |
| + | while (p++, isspace(*p)) |
| + | expr_len--; |
| + | } else { |
| + | p++; |
| + | } |
| + | } |
| + | /* There can be no more than expr_len/2 |
| + | * integers/names in any given correct or incorrect expression. |
| + | * (modulo "09v09v09v09v09v" case, |
| + | * but we have code to detect that early) |
| + | */ |
| + | numstackptr = numstack = alloca((expr_len / 2) * sizeof(numstack[0])); |
| + | opstackptr = opstack = alloca(expr_len * sizeof(opstack[0])); |
| + | } |
| /* Start with a left paren */ | |
| dbg("(%d) op:TOK_LPAREN", (int)(opstackptr - opstack)); | |