What would cause std::cout to lose some characters in my string

Question

I am calling std::cout as so:

 cout << "will " << tempLine << " be put in the table??" << endl;

but my output is like this:

 be put in the table??

I feel like templine might have a '\0' character in it which stops std::cout working correctly. Would this cause said output?

I will put my code underneath for reference:

#include <stdio.h> #include <stdlib.h> #include <iostream> #include <fstream> #include <string> #include <map> using namespace std; int tempVarInst; int tempVarDest; int tempVarJmp = 0; int lineCount=0; map<string, int> symbolTable; bool replace(std::string& str, const std::string& from, const std::string& to) { size_t start_pos = str.find(from); if(start_pos == std::string::npos) return false; str.replace(start_pos, from.length(), to); return true; } bool isComment(string line){ string comment = "/"; if((line.find(comment)) != string::npos){ return true; }else{ return false; } } string ConvertToBinary(unsigned int val) { string tempStore; unsigned int mask = 1 << (sizeof(int) * 4 - 1); for(int i = 0; i < sizeof(int) * 4; i++){ if( (val & mask) == 0 ) tempStore+='0'; else tempStore+='1'; mask >>= 1; } return tempStore; } bool isMemLoc(string line){ string symbol = "@"; if(line.find(symbol) != string::npos ){ return true; }else{ return false; } } int destConstants(string line){ if(line== "A") return 32; if(line== "M") return 8; if(line== "D") return 16; if(line== "AM") return 40; if(line== "AD") return 48; if(line== "MD") return 24; if(line== "AMD") return 56; } int isInst(string line){ if(line=="0") return 60032; if(line=="1") return 61376; if(line=="-1") return 61056; if(line=="D") return 58112; if(line=="!D") return 58176; if(line=="M") return 64512; if(line=="A") return 60416; if(line=="!M") return 64576; if(line=="!A") return 60480; if(line=="-D") return 58304; if(line=="-M") return 64704; if(line=="-A") return 60608; if(line=="D+1") return 59328; if(line== "M+1") return 64960; if(line== "A+1") return 60864; if(line== "D-1") return 58240; if(line== "M-1") return 64640; if(line== "A-1") return 60544; if(line== "D+M") return 61568; if(line== "D+A") return 57472; if(line== "D-M") return 62656; if(line== "D-A") return 58560; if(line== "M-D") return 61888; if(line== "A-D") return 57792; if(line== "D&M") return 61440; if(line== "D&A") return 57344; if(line== "D|M") return 62784; if(line== "D|A") return 58688; } int jmpConstants(string line){ if(line== "JGT") return 1; if(line== "JEQ") return 2; if(line== "JGE") return 3; if(line== "JLT") return 4; if(line== "JNE") return 5; if(line== "JLE") return 6; if(line== "JMP") return 7; } bool isJumpInstruction(string line){ string symbol = ";"; if(line.find(symbol) != string::npos ){ return true; }else{ return false; } } void firstPass(ifstream &infile){ string tempLine; int iterator=0; while (getline(infile, tempLine)){ if(tempLine.substr(0,1) == "("){ cout << "will " << tempLine << " be put in the table??" << endl; //////////////////////////////////// for (map<string, int>::iterator it = symbolTable.begin(); it != symbolTable.end(); ++it) { cout << "ASDJASJASDJJSJAS: " << it->first << endl; if (it->first == tempLine) continue; else { symbolTable.insert(pair<string, int>(tempLine, lineCount)); lineCount++; } } ///////////////////////////// for (map<string, int>::iterator it = symbolTable.begin(); it != symbolTable.end(); ++it) { cout << "HERE The Symbol Table is: "<< it->first << " " << it->second << endl; } } else lineCount++; } cout << "end file" << endl; } int main( int argc, const char* argv[] ) { string outLine; string file1 = argv[1]; replace(file1, "asm", "hack"); //input //WHILE READ LINE() ifstream infile(argv[1]); string tempLine; ofstream outfile(file1.c_str()); tempVarJmp=0; tempVarDest=0; tempVarInst=0; firstPass(infile); ifstream secondPass(argv[1]); ofstream secondOut(file1.c_str()); cout << "hi" << endl; while (getline(secondPass, tempLine)){ //cout << "current line: " << tempLine << " length: " << tempLine.length() << endl; tempLine = tempLine.substr(0, tempLine.length()-1); //Blank check //cout << "The tempLine is: " << tempLine << endl; if(tempLine.length()<=1){ //cout << "Checking blackspaces, tempLine is: " << tempLine << endl; continue; } //Comment Check else if(isComment(tempLine)){ //cout << "Checking comments, tempLine is: " << tempLine << endl; continue; } //@ Check else if(isMemLoc(tempLine)){ tempLine.erase(0,1); int number = (atoi(tempLine.c_str())); //cout << "number: " << number << "binary: "<< ConvertToBinary(number) << endl; outfile << ConvertToBinary(number) << std::endl; continue; } //tempLine=tempLine(isInst).c_str+tempLine(destConstants)+tempLine(jmpConstants); //outfile << ConvertToBinary(tempLine) << endl; else if(isJumpInstruction(tempLine)){ // cout << "Jump Instruction" << endl; tempVarJmp = jmpConstants(tempLine.substr(tempLine.find(';')+1, tempLine.length())); cout << tempLine << " " << tempLine.length(); // cout << "TempVarInst: " << tempLine.substr(tempLine.find(';')+1) << endl; // cout << "tempVarJmp: " << tempVarJmp << endl; tempVarDest = isInst(tempLine.substr(0,tempLine.find(';'))); // cout << "tempvarDest = " << tempVarDest << endl; int finalVal=tempVarDest+tempVarJmp; outfile << ConvertToBinary(finalVal) << std::endl; /// cout << "TempVarJmp is: " << tempVarJmp << endl; // cout << "output should be: " << ConvertToBinary(finalVal) << endl; //cout << ConvertToBinary(finalVal) << endl; }else{ // cout << "Right TempLineInst is: " << tempLine.substr(tempLine.find('=')+1,tempLine.length()) << endl; // cout << "Right TempLineDest is: " << tempLine.substr(0,tempLine.find('=')) << endl; tempVarInst = isInst(tempLine.substr(tempLine.find('=')+1,tempLine.length())); tempVarDest = destConstants(tempLine.substr(0,tempLine.find('='))); tempVarJmp = 0; if(tempLine.substr(1,2) == ";J"){ tempVarJmp = jmpConstants(tempLine.substr(2,4)); // cout << "TempLineDest is: " << tempLine.substr(2,4) << endl; } //cout << "tempvarInst = " << tempVarInst << endl; //cout << "tempvarDest = " << tempVarDest << endl; //cout << "tempvarJmp = " << tempVarJmp << endl; int totalSum = tempVarInst+tempVarDest+tempVarJmp; //cout << "totalSum: " << ConvertToBinary(totalSum) << endl; outfile << ConvertToBinary(totalSum) << std::endl; } } outfile.close(); }

It's likely the file has CRLF line endings and you're not on Windows. — Qaz
– Qaz, Commented Jun 6, 2015 at 3:35
I am running on Red Hat Linux at the moment, is there an easy to fix this in code ie ignore CRLF line endings? — Barney Chambers
– Barney Chambers, Commented Jun 6, 2015 at 3:37
@BarneyChambers, Remove carriage return characters from the (end of the) string? — Qaz
– Qaz, Commented Jun 6, 2015 at 3:38

Tony Delroy · Accepted Answer · 2015-06-06 03:38:59Z

Whether NUL could somehow prevent or clear input depends on your terminal program. A carriage return (ASCII code 13) is an even stronger candidate for the cause, as it's almost universally handled by terminals returning to the left-most column on the current line.

To find out, I suggest you write a function that outputs a string one character at a time, using escaping (in octal for control characters) much as you can use when specifying string literals in your program:

if (c == '"' || c == '\') os << '\\'; if (std::isprint(c)) os << c; else os << '\\' << std::setw(3) << std::setfill('0') << std::oct << (int)(unsigned char)c;

+1 for a constructive way to analyze the cause of the problem. (breakpoint and watching the content of templine would also do the job,btw.)
What makes octal such a desirable choice here? Maybe it's me, but I'm not familiar with the octal representations of control characters at all.
@chris: good question - I have no idea why octal became popular, but now it's kind of traditional for C and consequently C++. A dozen or so characters have better known escape sequences like \r for carriage return and \t for a horizontal tab, but octal conveniently covers all ASCII characters. Support for hex is now required by the Standard ala \x12 - I'm not sure why they didn't add some notation for decimal too. Perhaps more people knowing their 8 times tables makes it easier than hex, if you do need to convert back to decimal.

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