CODEWITHSUNDEEP
c++linuxgcc
dimba
dimba

Reputation: 27581

gcc - removing "is used uninitialized in this function" warning

Cleaning code from warning after adding -O2 -Wall flags to gcc (4.4.6). I have a lot of warning in some legacy code. This is very simplified version to demonstrate the problem:

 1 #include <cstdio>
  2
  3 bool init(bool& a)
  4 {
  5     return true;
  6 }
  7
  8 int main()
  9 {
 10     bool a;
 11
 12     if (!init(a))
 13     {
 14         return 1;
 15     }
 16
 17     if (a)
 18     {
 19         printf("ok\n");
 20     }
 21 }

When compiling it as "gcc main.cpp -O2 -Wall" I receive:

 main.cpp:17: warning: `a' is used uninitialized in this function

In real code, init() returns true only if it initializes "a", so there's virually no use by uninitialized "a".

Whan can be done to fix the warning.

Upvotes: 8

Views: 57404

Answers (4)

Daniel Frey
Daniel Frey

Reputation: 56863

If you don't want to initialize the variable with some value, you can use GCC's diagnostic pragmas:

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wuninitialized"
   if( a )
#pragma GCC diagnostic pop

This might be handy if your code has performace issues when everything would be initialized. In your example, of course, using bool a = false; is clearly the better choice.

Upvotes: 13

tristan
tristan

Reputation: 4322

add -Wno-uninitialized to your compile option

Upvotes: 2

fen
fen

Reputation: 10115

int main()
{
    bool a = false;
    ...

Initialize all variables, always!

Upvotes: 6

Zac Wrangler
Zac Wrangler

Reputation: 1445

change bool a; to bool a = false; will remove this warning.

The compiler wont know init(a) is meant to 'initialize a', it only sees the program tries to call a function with a uninitialized variable.

Upvotes: 13

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