0

I recently had an issue with a program where I compared a variable that I had initialized with one that hadn't. I figured it out (with the help of others here!) eventually, but this raised another question. Is the value of an uninitialized variable set by the compiler or by something else entirely. When I ran the program in Linux, the variable was set to -127xxxxxx, however, in Windows it was set to 0.

So essentially my question is what sets the value of variables with no values. This was a C program.

OS: Windows 10 and Linux Ubuntu 14.04.5 LTS

Hunter
  • 109
  • 1
  • 6
  • @KyleStrand Thank you, that post was a similarly different question, but one of the answers on that post answered my question. – Hunter Feb 24 '17 at 03:08

1 Answers1

1

In C, uninitialized block scope variables are said to have indeterminate value. If you write code that tries to read an indeterminate value then, depending on a few details about the systems and the rest of the code, either:

  • undefined behaviour happens immediately, or
  • The read produces some value which may appear to change for no reason, and will cause undefined behaviour if that value (or a value derived from it) is passed to a library function.
Community
  • 1
  • 1
M.M
  • 138,810
  • 21
  • 208
  • 365