Language: C++

#include <bits/stdc++.h>
using namespace std;
#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) begin(a),end(a)
#define MS(m,v) memset(m,v,sizeof(m))
#define D10  fixed<<setprecision(5)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<short, short> P;
typedef complex<double> Point;
typedef long long ll;
const int INF = 114514810;
const int MOD = 100000007;
const double EPS = 1e-10;
const double PI = acos(-1.0);
struct edge
{
	int from, to, cost;
	bool operator < (const edge& e) const { return cost < e.cost; }
	bool operator >(const edge& e) const { return cost > e.cost; }
};
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///

int calc(string s)
{
	vi v;
	REP(i, s.size())
	{
		if (s[i] == '+') v.push_back(0);
		else if (s[i] == '-') v.push_back(1);
		else if (s[i] == '*') v.push_back(2);
		else if (s[i] == '/') v.push_back(3);
		else
		{
			int tmp = s[i] - '0';
			int t = i+1;
			while (isdigit(s[t]))
			{
				tmp = tmp * 10 + s[t] - '0';
				t++;
			}
			i = t - 1;
			v.push_back(tmp);
		}
	}

	while (v.size() > 1)
	{
		for (int i = 1; i < v.size();i+=2)
		{
			if (v[i]==2)
			{
				int tmp = v[i - 1] * v[i + 1];
				v[i - 1] = tmp;
				v.erase(v.begin() + i + 1);
				v.erase(v.begin() + i);
				goto next;
			}
			else if (v[i] == 3)
			{
				int tmp = v[i - 1] / v[i + 1];
				v[i - 1] = tmp;
				v.erase(v.begin() + i + 1);
				v.erase(v.begin() + i);
				goto next;
			}
		}
		for (int i = 1; i < v.size(); i += 2)
		{
			if (v[i] == 0)
			{
				int tmp = v[i - 1] + v[i + 1];
				v[i - 1] = tmp;
				v.erase(v.begin() + i + 1);
				v.erase(v.begin() + i);
				break;
			}
			else if (v[i] == 1)
			{
				int tmp = v[i - 1] - v[i + 1];
				v[i - 1] = tmp;
				v.erase(v.begin() + i + 1);
				v.erase(v.begin() + i);
				break;
			}
		next:;
		}
	}
	return v[0];
}

int solve(string s)
{
	while (1)
	{
		if (find(ALL(s), '(') == s.end())
		{
			return calc(s);
		}
		else
		{
			string tmp;
			REP(i, s.size())
			{
				if (s[i] != '(') tmp.push_back(s[i]);
				else
				{
					int j;
					for (j = s.size()-1;; j--)
					{
						if (s[j] == ')')
						{
							int t = solve(s.substr(i+1, j - i - 1));
							tmp += to_string(t);
							break;
						}
					}
					i = j;
				}
			}
			return solve(tmp);
		}
	}
	return 0;
}

int main()
{
	int sets;
	string s;
	cin >> sets;
	REP(set, sets)
	{
		cin >> s;
		s.erase(s.size() - 1);
		cout << solve(s) << endl;
	}
	return 0;
}

Compiler output:
a.cc: In function 'int calc(std::string)':
a.cc:89:17: error: jump to label 'next'
   89 |                 next:;
      |                 ^~~~
a.cc:68:38: note:   from here
   68 |                                 goto next;
      |                                      ^~~~
a.cc:71:26: note:   crosses initialization of 'int i'
   71 |                 for (int i = 1; i < v.size(); i += 2)
      |                          ^
a.cc:89:17: error: jump to label 'next'
   89 |                 next:;
      |                 ^~~~
a.cc:60:38: note:   from here
   60 |                                 goto next;
      |                                      ^~~~
a.cc:71:26: note:   crosses initialization of 'int i'
   71 |                 for (int i = 1; i < v.size(); i += 2)
      |                          ^