static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int ec_GFp_nist_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,\n                          BN_CTX *ctx)\n{\n    int ret = 0;\n    BN_CTX *ctx_new = NULL;\n    if (!group || !r || !a) {\n        ECerr(EC_F_EC_GFP_NIST_FIELD_SQR, EC_R_PASSED_NULL_PARAMETER);\n        goto err;\n    }\n    if (!ctx)\n        if ((ctx_new = ctx = BN_CTX_new()) == NULL)\n            goto err;\n    if (!BN_sqr(r, a, ctx))\n        goto err;\n    if (!group->field_mod_func(r, r, group->field, ctx))\n        goto err;\n    ret = 1;\n err:\n    BN_CTX_free(ctx_new);\n    return ret;\n}', 'int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)\n{\n    int ret = bn_sqr_fixed_top(r, a, ctx);\n    bn_correct_top(r);\n    bn_check_top(r);\n    return ret;\n}', 'int bn_sqr_fixed_top(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)\n{\n    int max, al;\n    int ret = 0;\n    BIGNUM *tmp, *rr;\n    bn_check_top(a);\n    al = a->top;\n    if (al <= 0) {\n        r->top = 0;\n        r->neg = 0;\n        return 1;\n    }\n    BN_CTX_start(ctx);\n    rr = (a != r) ? r : BN_CTX_get(ctx);\n    tmp = BN_CTX_get(ctx);\n    if (rr == NULL || tmp == NULL)\n        goto err;\n    max = 2 * al;\n    if (bn_wexpand(rr, max) == NULL)\n        goto err;\n    if (al == 4) {\n#ifndef BN_SQR_COMBA\n        BN_ULONG t[8];\n        bn_sqr_normal(rr->d, a->d, 4, t);\n#else\n        bn_sqr_comba4(rr->d, a->d);\n#endif\n    } else if (al == 8) {\n#ifndef BN_SQR_COMBA\n        BN_ULONG t[16];\n        bn_sqr_normal(rr->d, a->d, 8, t);\n#else\n        bn_sqr_comba8(rr->d, a->d);\n#endif\n    } else {\n#if defined(BN_RECURSION)\n        if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) {\n            BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL * 2];\n            bn_sqr_normal(rr->d, a->d, al, t);\n        } else {\n            int j, k;\n            j = BN_num_bits_word((BN_ULONG)al);\n            j = 1 << (j - 1);\n            k = j + j;\n            if (al == j) {\n                if (bn_wexpand(tmp, k * 2) == NULL)\n                    goto err;\n                bn_sqr_recursive(rr->d, a->d, al, tmp->d);\n            } else {\n                if (bn_wexpand(tmp, max) == NULL)\n                    goto err;\n                bn_sqr_normal(rr->d, a->d, al, tmp->d);\n            }\n        }\n#else\n        if (bn_wexpand(tmp, max) == NULL)\n            goto err;\n        bn_sqr_normal(rr->d, a->d, al, tmp->d);\n#endif\n    }\n    rr->neg = 0;\n    rr->top = max;\n    rr->flags |= BN_FLG_FIXED_TOP;\n    if (r != rr && BN_copy(r, rr) == NULL)\n        goto err;\n    ret = 1;\n err:\n    bn_check_top(rr);\n    bn_check_top(tmp);\n    BN_CTX_end(ctx);\n    return ret;\n}', 'void BN_CTX_start(BN_CTX *ctx)\n{\n    CTXDBG("ENTER BN_CTX_start()", ctx);\n    if (ctx->err_stack || ctx->too_many)\n        ctx->err_stack++;\n    else if (!BN_STACK_push(&ctx->stack, ctx->used)) {\n        BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);\n        ctx->err_stack++;\n    }\n    CTXDBG("LEAVE BN_CTX_start()", ctx);\n}', 'void BN_CTX_end(BN_CTX *ctx)\n{\n    CTXDBG("ENTER BN_CTX_end()", ctx);\n    if (ctx->err_stack)\n        ctx->err_stack--;\n    else {\n        unsigned int fp = BN_STACK_pop(&ctx->stack);\n        if (fp < ctx->used)\n            BN_POOL_release(&ctx->pool, ctx->used - fp);\n        ctx->used = fp;\n        ctx->too_many = 0;\n    }\n    CTXDBG("LEAVE BN_CTX_end()", ctx);\n}', 'static unsigned int BN_STACK_pop(BN_STACK *st)\n{\n    return st->indexes[--(st->depth)];\n}']