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c++ - 调试 c++ 运行时错误的好方法是什么？

问题描述

调试以下问题的好方法是什么？

我尝试在 ubuntu 中运行代码的 Clion 中使用地址清理程序并设置断点。它们都没有提供有用的调试消息来定位问题。

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/stl_vector.h:1043:34

来自此问题的以下代码可以重现运行时错误：

https://leetcode.com/problems/maximum-length-of-pair-chain/

#include <bits/stdc++.h>

using namespace std;


class Solution {
public:
    int findLongestChain(vector<vector<int>> &pairs) {


        int n = pairs.size();
        if (n == 0) return 0;
        sort(pairs.begin(), pairs.end(), [](vector<int>& a, vector<int>& b) { return a[1] <= b[1]; });


        int lastRight = pairs[0][1];
        int res = 1;
        for (int i = 1; i < n; i++) {
            if (pairs[i][0] > lastRight) {
                res++;
                lastRight = pairs[i][1];
            }

        }

        return res;

    }
};

int main() {

    vector<vector<int>> pairs = {{-994,-938},{19,592},{-232,-209},{788,937},{772,838},{741,801},{-229,747},{242,907},{-592,730},{-517,996},{380,693},{98,662},{-760,169},{-844,541},{-535,461},{-544,138},{-799,390},{-998,-965},{680,1000},{-73,698},{-955,51},{-909,-891},{-61,558},{217,357},{-721,108},{351,421},{608,903},{449,615},{-31,165},{979,998},{-849,-69},{627,974},{-880,918},{-766,209},{178,695},{266,917},{518,763},{-183,665},{878,996},{77,430},{-906,-403},{136,594},{-694,-525},{806,845},{-445,8},{-813,687},{-730,247},{909,925},{-360,741},{-418,-199},{-111,498},{367,873},{341,664},{-27,14},{-450,814},{-405,-117},{249,932},{703,864},{141,888},{278,646},{-851,-804},{-956,-819},{192,686},{-779,69},{-803,-502},{619,969},{-973,14},{-659,-136},{340,951},{-31,137},{-801,-701},{189,323},{107,615},{403,918},{452,753},{-224,-6},{697,959},{312,787},{-862,-398},{634,971},{-645,-148},{464,613},{570,592},{710,910},{-422,-139},{-148,360},{572,716},{905,909},{237,709},{-636,274},{-759,-693},{-937,112},{796,879},{-927,857},{-861,-767},{898,946},{667,719},{-234,-94},{259,911},{-870,-125},{-378,-138},{593,712},{-572,-219},{160,387},{-72,480},{870,943},{-182,669},{-713,-151},{-859,-524},{108,371},{-861,786},{17,579},{205,644},{-527,312},{752,933},{113,896},{-164,100},{-128,961},{-998,986},{551,757},{388,990},{-211,530},{853,886},{-174,762},{700,912},{-708,-655},{-414,793},{362,828},{556,850},{-501,-437},{39,215},{-311,-115},{-798,122},{965,995},{-84,246},{-469,-95},{581,841},{-625,-430},{347,561},{-969,-43},{362,412},{-829,850},{-17,571},{-763,784},{-591,776},{700,877},{619,855},{-222,895},{-340,436},{-651,-9},{-836,-361},{458,987},{653,975},{-105,-66},{261,924},{715,803},{107,235},{809,958},{17,46},{-856,140},{-311,835},{-185,146},{-348,200},{338,662},{170,495},{687,902},{-889,-622},{-886,-117},{-11,679},{-496,196},{-314,-242},{-238,194},{510,658},{237,826},{-977,505},{-326,311},{-207,416},{563,979},{-526,536},{698,843},{522,829},{135,505},{-959,253},{19,258},{-945,-105},{-229,906},{798,978},{-857,-452},{-56,320},{309,649},{143,328},{-195,-8},{-464,320},{-172,13},{68,332},{-713,-74},{936,966},{276,860},{-425,334},{-461,730},{852,938},{-828,-818},{-562,-6},{-722,723},{945,975},{165,989},{-629,274},{484,486},{977,995},{-378,263},{3,836},{-661,-558},{-384,839},{-783,237},{719,795},{-52,768},{521,949},{-235,107},{846,885},{-257,159},{-447,461},{202,550},{902,977},{558,983},{830,882},{-174,631},{-424,926},{248,521},{107,173},{97,738},{-593,-441},{302,435},{703,792},{-994,308},{-543,926},{-794,398},{936,984},{-422,-107},{-122,982},{834,836},{-694,63},{341,755},{442,672},{-866,647},{545,978},{352,700},{73,635},{-201,-123},{-237,140},{-395,205},{921,968},{-806,166},{-951,256},{436,863},{-996,-435},{853,907},{-999,-686},{443,506},{788,827},{-133,238},{-630,284},{934,939},{-385,536},{387,637},{547,565},{919,927},{-271,742},{-263,141},{-359,712},{-323,-18},{494,674},{348,526},{-537,-437},{911,935},{936,953},{15,829},{-666,874},{-808,496},{-393,366},{957,974},{681,961},{-747,-420},{-713,-213},{445,782},{900,952},{348,562},{-929,957},{622,667},{725,837},{177,931},{959,969},{-156,466},{680,966},{-869,-822},{313,785},{-627,469},{-313,518},{-626,498},{29,754},{83,386},{-502,506},{-672,647},{-507,47},{393,553},{293,312},{-524,-100},{325,350},{-817,31},{-421,695},{-400,227},{-387,-9},{-556,412},{732,763},{-18,394},{-478,-370},{-326,-305},{254,997},{-341,837},{-727,859},{349,451},{-335,202},{-540,-481},{186,272},{647,975},{-281,919},{284,758},{-500,58},{464,828},{479,628},{828,1000},{-500,-132},{-41,532},{734,995},{3,232},{-358,185},{669,807},{-524,501},{-240,608},{75,683},{833,923},{-454,917},{707,858},{322,651},{887,974},{63,263},{-705,462},{-606,366},{-792,-699},{5,315},{265,573},{-735,461},{632,755},{250,329},{861,915},{-93,577},{-107,-2},{164,313},{-222,72},{165,343},{600,639},{-954,-355},{682,700},{195,387},{263,649},{532,642},{732,919},{-321,-219},{423,701},{-2,638},{-697,591},{474,921},{266,481},{-80,51},{305,906},{-265,242},{896,963},{-930,120},{877,932},{453,599},{-851,486},{-571,-28},{-659,597},{-72,978},{-494,385},{686,797},{40,874},{-245,115},{23,680},{-950,34},{-763,558},{464,786},{-4,566},{-289,-102},{92,799},{628,887},{301,813},{355,414},{-452,865},{41,587},{816,983},{887,953},{-4,753},{-112,10},{12,554},{-1000,994},{-332,142},{653,965},{419,453},{612,687},{-205,877},{-931,-548},{-686,61},{371,944},{-740,837},{-622,196},{-604,-45},{913,957},{741,808},{355,470},{666,938},{-79,235},{53,126},{-250,5},{40,584},{806,975},{-29,416},{352,835},{-914,-733},{-171,809},{651,935},{-893,-364},{33,433},{506,856},{682,725},{-380,476},{-542,-135},{478,571},{-986,13},{871,947},{698,845},{-255,259},{-52,247},{-953,494},{920,964},{-996,622},{249,858},{243,739},{199,644},{467,862},{-262,-130},{754,908},{-408,990},{885,951},{978,996},{-506,740},{-437,536},{542,750},{695,891},{564,601},{-388,760},{257,908},{348,615},{558,989},{106,214},{-163,922},{396,788},{-980,-381},{-477,450},{-144,741},{551,770},{642,979},{-91,314},{595,840},{-391,349},{-751,541},{618,912},{9,213},{953,962},{-377,728},{-53,566},{-809,485},{-275,111},{221,658},{340,903},{-964,448},{279,554},{666,742},{-818,-13},{934,963},{-396,877},{320,472},{-257,-186},{536,927}};


    cout << Solution().findLongestChain(pairs);

}

编辑：初衷是寻求调试工具的建议。对于给出的示例问题，似乎不存在这样的工具。

标签： c++debuggingaddress-sanitizer

解决方案

一个问题是这样的：

sort(pairs.begin(), pairs.end(), [](vector<int>& a, vector<int>& b) 
 { return a[1] <= b[1]; });  // <-- Not a strict-weak-ordering.

排序标准必须是严格弱排序。任何有<=或>=总是怀疑违反此规则的排序标准。违反严格-弱序规则会导致未定义的行为。

解决方法是比较该项目严格小于另一个项目。

sort(pairs.begin(), pairs.end(), [](vector<int>& a, vector<int>& b) 
 { return a[1] < b[1]; });

请注意：

如果您使用的是 Visual Studio，则调试运行时会针对此类违规进行精确检查。比较函数被调用两次，第一次使用 A,B 顺序，第二次使用 B,A 顺序。每次调用的返回值都会进行比较，如果有违规将发生 assert()。

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