static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int ec_GFp_simple_group_set_curve(EC_GROUP *group,\n                                  const BIGNUM *p, const BIGNUM *a,\n                                  const BIGNUM *b, BN_CTX *ctx)\n{\n    int ret = 0;\n    BN_CTX *new_ctx = NULL;\n    BIGNUM *tmp_a;\n    if (BN_num_bits(p) <= 2 || !BN_is_odd(p)) {\n        ECerr(EC_F_EC_GFP_SIMPLE_GROUP_SET_CURVE, EC_R_INVALID_FIELD);\n        return 0;\n    }\n    if (ctx == NULL) {\n        ctx = new_ctx = BN_CTX_new();\n        if (ctx == NULL)\n            return 0;\n    }\n    BN_CTX_start(ctx);\n    tmp_a = BN_CTX_get(ctx);\n    if (tmp_a == NULL)\n        goto err;\n    if (!BN_copy(group->field, p))\n        goto err;\n    BN_set_negative(group->field, 0);\n    if (!BN_nnmod(tmp_a, a, p, ctx))\n        goto err;\n    if (group->meth->field_encode) {\n        if (!group->meth->field_encode(group, group->a, tmp_a, ctx))\n            goto err;\n    } else if (!BN_copy(group->a, tmp_a))\n        goto err;\n    if (!BN_nnmod(group->b, b, p, ctx))\n        goto err;\n    if (group->meth->field_encode)\n        if (!group->meth->field_encode(group, group->b, group->b, ctx))\n            goto err;\n    if (!BN_add_word(tmp_a, 3))\n        goto err;\n    group->a_is_minus3 = (0 == BN_cmp(tmp_a, group->field));\n    ret = 1;\n err:\n    BN_CTX_end(ctx);\n    BN_CTX_free(new_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}']