static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int BN_generate_prime_ex(BIGNUM *ret, int bits, int safe,\n                         const BIGNUM *add, const BIGNUM *rem, BN_GENCB *cb)\n{\n    BIGNUM *t;\n    int found = 0;\n    int i, j, c1 = 0;\n    BN_CTX *ctx = NULL;\n    prime_t *mods = NULL;\n    int checks = BN_prime_checks_for_size(bits);\n    if (bits < 2) {\n        BNerr(BN_F_BN_GENERATE_PRIME_EX, BN_R_BITS_TOO_SMALL);\n        return 0;\n    } else if (bits == 2 && safe) {\n        BNerr(BN_F_BN_GENERATE_PRIME_EX, BN_R_BITS_TOO_SMALL);\n        return 0;\n    }\n    mods = OPENSSL_zalloc(sizeof(*mods) * NUMPRIMES);\n    if (mods == NULL)\n        goto err;\n    ctx = BN_CTX_new();\n    if (ctx == NULL)\n        goto err;\n    BN_CTX_start(ctx);\n    t = BN_CTX_get(ctx);\n    if (t == NULL)\n        goto err;\n loop:\n    if (add == NULL) {\n        if (!probable_prime(ret, bits, mods))\n            goto err;\n    } else {\n        if (safe) {\n            if (!probable_prime_dh_safe(ret, bits, add, rem, ctx))\n                goto err;\n        } else {\n            if (!bn_probable_prime_dh(ret, bits, add, rem, ctx))\n                goto err;\n        }\n    }\n    if (!BN_GENCB_call(cb, 0, c1++))\n        goto err;\n    if (!safe) {\n        i = BN_is_prime_fasttest_ex(ret, checks, ctx, 0, cb);\n        if (i == -1)\n            goto err;\n        if (i == 0)\n            goto loop;\n    } else {\n        if (!BN_rshift1(t, ret))\n            goto err;\n        for (i = 0; i < checks; i++) {\n            j = BN_is_prime_fasttest_ex(ret, 1, ctx, 0, cb);\n            if (j == -1)\n                goto err;\n            if (j == 0)\n                goto loop;\n            j = BN_is_prime_fasttest_ex(t, 1, ctx, 0, cb);\n            if (j == -1)\n                goto err;\n            if (j == 0)\n                goto loop;\n            if (!BN_GENCB_call(cb, 2, c1 - 1))\n                goto err;\n        }\n    }\n    found = 1;\n err:\n    OPENSSL_free(mods);\n    if (ctx != NULL)\n        BN_CTX_end(ctx);\n    BN_CTX_free(ctx);\n    bn_check_top(ret);\n    return found;\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}']