A warning – comparison between signed and unsigned integer expressions

It is usually a good idea to declare variables as unsigned or size_t if they will be compared to sizes, to avoid this issue. Whenever possible, use the exact type you will be comparing against (for example, use std::string::size_type when comparing with a std::string‘s length).

Compilers give warnings about comparing signed and unsigned types because the ranges of signed and unsigned ints are different, and when they are compared to one another, the results can be surprising. If you have to make such a comparison, you should explicitly convert one of the values to a type compatible with the other, perhaps after checking to ensure that the conversion is valid. For example:

unsigned u = GetSomeUnsignedValue();
int i = GetSomeSignedValue();

if (i >= 0)
{
    // i is nonnegative, so it is safe to cast to unsigned value
    if ((unsigned)i >= u)
        iIsGreaterThanOrEqualToU();
    else
        iIsLessThanU();
}
else
{
    iIsNegative();
}

Related Posts:

  1. How to create a dynamic array of integers
  2. How to implement 2D vector array?
  3. What is the difference between g++ and gcc?
  4. g++ ld: symbol(s) not found for architecture x86_64
  5. Making my own toString() method on c++ struct
  6. Struct Constructor in C++?
  7. What is meant with “const” at end of function declaration? [duplicate]
  8. What’s the C++ version of Java’s ArrayList
  9. What is the difference between “long”, “long long”, “long int”, and “long long int” in C++?
  10. ‘g++’ is not recognized as an internal or external command, operable program or batch file
  11. How do I convert a double into a string in C++?
  12. How to create timer events using C++ 11?
  13. How to concatenate two strings in C++?
  14. ‘g++’ is not recognized as an internal or external command, operable program or batch file
  15. Read file line by line using ifstream in C++
  16. Virtual/pure virtual explained
  17. error: lvalue required as unary & operand
  18. What is use of c_str function In c++
  19. Is there a decent wait function in C++?
  20. What does T&& (double ampersand) mean in C++11?
  21. C++ – No matching member function for call to ‘push_back’
  22. error: lvalue required as unary & operand
  23. C/C++ JSON parser
  24. C++ Parsing input string to variables
  25. ‘cout’ was not declared in this scope
  26. Segmentation fault error 11 C++
  27. Why doesn’t C++ have a garbage collector?
  28. How does ifstream’s eof() work?
  29. terminate called after throwing an instance of ‘std::invalid_argument’ what(): stoi
  30. Why would we call cin.clear() and cin.ignore() after reading input?
  31. Should I learn C before learning C++?
  32. Comparison with string literal results in unspecified behaviour?
  33. c++: No instance of overloaded function
  34. C++ error: Undefined symbols for architecture x86_64
  35. Visual Studio debugger error: Unable to start program Specified file cannot be found
  36. Printing the correct number of decimal points with cout
  37. libstdc++-6.dll not found
  38. Callback functions in C++
  39. Reading from text file until EOF repeats last line
  40. How does std::forward work? [duplicate]
  41. Examples of good gotos in C or C++
  42. Sleep function in C++
  43. Undefined reference to class constructor, including .cpp file fixes
  44. Deleting a dynamically allocated 2D array
  45. How to add element to C++ array?
  46. Difference of keywords ‘typename’ and ‘class’ in templates?
  47. Error: Jump to case label in switch statement
  48. What does int & mean
  49. Split a string into an array in C++
  50. splitting a string into an array in C++ without using vector
  51. Remove spaces from std::string in C++
  52. How to use glOrtho() in OpenGL?
  53. error: ‘ostream’ does not name a type
  54. Remove spaces from std::string in C++
  55. Read data from a file into an array – C++
  56. Unknown override specifier, missing type specifier
  57. error: overloaded ‘operator<<' must be a binary operator (has 3 parameters)
  58. What is the preferred way to include error messages in C++?
  59. How to Convert a C++ String to Uppercase
  60. C++ Fractions Class
  61. #pragma once vs include guards?
  62. Debug vs Release in CMake
  63. C++ Remove punctuation from String
  64. prototype for “….” does not match any in class “…”
  65. Cannot open Windows.h in Microsoft Visual Studio
  66. Nested For – Loops to create multiplication table C++
  67. Warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11?
  68. Reference to non-static member function must be called
  69. Call to non-static member function without an object argument compiler error
  70. How can I assign an array from an initializer list?
  71. I get this error: “glibc detected”
  72. How can I get and use the header file in my C++ program?
  73. cin.eof() functionality
  74. Implementing a tree in C++
  75. Drawing Circle with OpenGL
  76. Run-Time Check Failure #2 – Stack around the variable ‘foo’ was corrupted
  77. How to implement “Press Any Key To Exit”
  78. Reading and writing binary file
  79. GCC -fPIC option
  80. got “cannot appear in a constant-expression” when using template
  81. C++ ostream and ofstream conversions
  82. C++ discards qualifiers
  83. What is the source of the data for the ProgramFiles, ProgramW6432Dir, ProgramFilesDir (x86), CommonProgramFiles environment variables?
  84. C++ : Exception occurred in script: basic_string::_S_construct NULL not valid
  85. Xcode 11.1: iostream’ file not found
  86. non-member function cannot have cv-qualifier
  87. too many initializers for ‘int [0]’ c++
  88. function does not take 1 arguments c++
  89. overloaded function with no contextual type information
  90. How exactly do lookup tables work and how to implement them?
  91. Multiple inputs on one line
  92. Why do I get: -9223372036854775808
  93. Return a 2d array from a function
  94. Linker error: “linker input file unused because linking not done”, undefined reference to a function in that file
  95. What is the difference among ios::app, out, and trunc in c++?
  96. Where can I find ‘winmm.lib’ (I’m using Visual Studio 2012)
  97. What is a `char*`?
  98. Does static constexpr variable inside a function make sense?
  99. “Incomplete type not allowed ” when creating std::ofstream objects
  100. Getting the error floating point exception: 8

Leave a Comment