static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int test_gf2m_mod_div(BIO *bp, BN_CTX *ctx)\n{\n    BIGNUM *a, *b[2], *c, *d, *e, *f;\n    int i, j, ret = 0;\n    int p0[] = { 163, 7, 6, 3, 0, -1 };\n    int p1[] = { 193, 15, 0, -1 };\n    a = BN_new();\n    b[0] = BN_new();\n    b[1] = BN_new();\n    c = BN_new();\n    d = BN_new();\n    e = BN_new();\n    f = BN_new();\n    BN_GF2m_arr2poly(p0, b[0]);\n    BN_GF2m_arr2poly(p1, b[1]);\n    for (i = 0; i < num0; i++) {\n        BN_bntest_rand(a, 512, 0, 0);\n        BN_bntest_rand(c, 512, 0, 0);\n        for (j = 0; j < 2; j++) {\n            BN_GF2m_mod_div(d, a, c, b[j], ctx);\n            BN_GF2m_mod_mul(e, d, c, b[j], ctx);\n            BN_GF2m_mod_div(f, a, e, b[j], ctx);\n            if (!BN_is_one(f)) {\n                fprintf(stderr, "GF(2^m) modular division test failed!\\n");\n                goto err;\n            }\n        }\n    }\n    ret = 1;\n err:\n    BN_free(a);\n    BN_free(b[0]);\n    BN_free(b[1]);\n    BN_free(c);\n    BN_free(d);\n    BN_free(e);\n    BN_free(f);\n    return ret;\n}', 'int BN_GF2m_mod_div(BIGNUM *r, const BIGNUM *y, const BIGNUM *x,\n                    const BIGNUM *p, BN_CTX *ctx)\n{\n    BIGNUM *xinv = NULL;\n    int ret = 0;\n    bn_check_top(y);\n    bn_check_top(x);\n    bn_check_top(p);\n    BN_CTX_start(ctx);\n    xinv = BN_CTX_get(ctx);\n    if (xinv == NULL)\n        goto err;\n    if (!BN_GF2m_mod_inv(xinv, x, p, ctx))\n        goto err;\n    if (!BN_GF2m_mod_mul(r, y, xinv, p, ctx))\n        goto err;\n    bn_check_top(r);\n    ret = 1;\n err:\n    BN_CTX_end(ctx);\n    return ret;\n}', 'void BN_CTX_start(BN_CTX *ctx)\n{\n    CTXDBG_ENTRY("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_EXIT(ctx);\n}', 'void BN_CTX_end(BN_CTX *ctx)\n{\n    CTXDBG_ENTRY("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_EXIT(ctx);\n}', 'static unsigned int BN_STACK_pop(BN_STACK *st)\n{\n    return st->indexes[--(st->depth)];\n}']