C++ 'std::bad_alloc' what(): std::bad_alloc - c++

Question

I am trying to run the below C++ code and I get this error :
Could anyone please help me clarify why is this the issue
Input : input/text_4.txt 9
terminate called after throwing an instance of 'std::bad_alloc' what(): std::bad_alloc
Aborted (core dumped)
After reading a few similar threads, the solution is to check dynamic memory allocation. However, my code does not have any dynamically allocated memory
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <sys/types.h>
#include <sys/stat.h>
using namespace std;
vector<string> arrangefile(vector<string>& scale, int width, int &number) {
int beginning = 0; int total = 0;
vector<string> result;
for(int i = 0; i < scale.size(); i++)
{
total += scale[i].size(); // add length of each word
if(total + i - beginning > width) // checking if the value has exceeded the maximum width
{
total -= scale[i].size();
string sentence= "",low="";
int last = i-1;
int space = width - total; // calculate number of spaces in each line
int check = max(last-beginning, 1);
int even = space/check;
while(even--){
low += " ";
}
int mod = space%check;
for(int j = beginning; j <= last; j++)
{
sentence += scale[j]; //find all values in a sentence
if(j < last || beginning == last)
sentence += low; // add the word low to the larger sentence
if(j - beginning < mod)
sentence += " ";
}
result.push_back(sentence); // add the sentence to the vector
number++; // counts the number of sentences
beginning = i;
total = scale[i].size();
}
}
string sentence =""; // for the last line
int last = scale.size()-1;
int check = last-beginning;
int space = width - total - check;
string low="";
while(space--){
low += " ";
}
for(int j = beginning; j <= last; j++)
{
sentence += scale[j];
if(j < last){
sentence += " ";
}
}
sentence += low;
result.push_back(sentence); // // add the sentence to the vector
number++; // counts the number of sentences
return result;
}
int main(){
string filepath, word;
int M, number=0;
cin >> filepath;
cin >> M;
ifstream fin;
fin.open(filepath.c_str());
unsigned found = filepath.find_last_of("/");
string b = filepath.substr(found+1);
int create = b.size();
string between = b.substr(0, create-4);
string final = between + "_formatted.txt";
string ending = "output/" + final;
mkdir ("output", 0777);
ofstream fout;
fout.open(ending);
for(int i = 0, count = 0; i<M; i++, count ++){
if(count == 9){
fout<<count;
count = -1;
}
else
fout<<count;
}
fout<<endl;
vector <string> first;
vector <string> second;
while(fin >> word){
first.push_back(word);
}
if(first.empty()){
cout<<"0 formatted lines written to "<< ending<<endl;
}
else{
second = arrangefile(first, M,number);
for (auto i = second.begin(); i != second.end(); ++i)
fout << *i <<endl;
cout<<number<<" formatted lines written to "<<ending<<endl;
}
fin.close();
fout.close();
return 0;
}
input file text_4.txt:
This is because not very many happy things happened
in the lives of the three Baudelaire youngsters.
Input: input/text_4.txt 8

Answer 1

When I run your code, on the i==16 iteration of the outer loop in arrangefile, we get width==8 and total==10, with check==1. As a result, even is initialized to -2, and so the while(even--) loop is (nearly) infinite. So it attempts to add spaces to low until it runs out of memory.
(Note that the memory used by std::string is dynamically allocated, so your code does have dynamic memory allocation. The same for std::vector.)
I haven't analyzed your algorithm closely enough to figure out the correct fix, but it's possible your loop should be while(even-- > 0) instead.
I'll second the tip in the comments to use your debugger, and I'll repost the link: What is a debugger and how can it help me diagnose problems?. That's how I found this bug.
I ran the program under the debugger gdb. It ran for a few seconds, at which point I got suspicious because the program doesn't appear do anything complicated enough to take that much computation time. So I interrupted the program (Ctrl-C) which let me see where it was and what it was doing. I could see that it was within the while(even--) loop. That was also suspicious because that loop should complete very fast. So I inspected the value of even (with the command p even) and saw that it was a large negative number. That could only happen if it had started as a negative number, which logically could only happen if total were greater than width. Inspecting their values I could see that this was indeed the case.
Maybe this will be helpful as you learn more about using your debugger.