VC++: fprintf error in release mode

Question

I'm working in visual studio 2010 and I have code written in C.

If i run in 'Debug' mode, the code will run without any error or warning.

But if I run the same in 'Release' mode, errors and warning will appear.

Error List:

        warning C4013:'fprintf' undefined; assuming extern returning int
        error C2065: 'stdout': undeclared identifier

What is the reason? please help

Possible duplicate of [What is an 'undeclared identifier' error and how do I fix it?](http://stackoverflow.com/questions/22197030/what-is-an-undeclared-identifier-error-and-how-do-i-fix-it) — Cody Gray, Nov 26 '16 at 14:09

score 2 · Answer 1 · answered Nov 04 '11 at 07:05

2

warning C4013:'fprintf' undefined; assuming extern returning int

It looks like you didn't include stdio.h.

answered Nov 04 '11 at 07:05

cnicutar

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Diana · Answer 2 · 2016-11-26T12:14:03.240

Seems like a difference in configuration between Release and Debug. Check the values for "Whole Program Optimization", they may differ between the two build configurations.

I had the same problem in reverse: In Release mode everything was fine, but in Debug mode some functions like 'ext' (FFTW library) were reported as "undefined; assuming extern returning int".

The failing build configuration (Release in my case) had under project properties Configuration Properties > General the option "Whole Program Optimization" set to No Whole Program Optimization.

The successful build configuration had this set to Use Link Time Code Generation. When I set that option in my failing target as well, everything worked fine.

VC++: fprintf error in release mode

2 Answers2