size_t different default value when running through VS2013 debugger vs CommandLine

Question

Running the following code via the visual studio debugger executes successfully. The "count" variable will be default initialized to 0.

If I run via the command line, i get random behaviour and my EXPECT_EQ( ... ) fails.

size_t expectedCount = actual.length() - expected.length();
position += 12;
size_t count;
for (size_t i = position ; i < actual.length(); ++i) {
    if (actual.at(i) == 'a')
        ++count;
}

EXPECT_EQ(expectedCount , count);

I'm assuming this is because Visual studio gives me a clean stack (everything is 0) whereas the commandline has lingering garbage?

score 3 · Accepted Answer · edited May 23 '17 at 12:00

3

In a function scope, the syntax size_t count; will not initialize a variable. Use size_t count{};

For more info on initialization, see Variable initialization in C++.

edited May 23 '17 at 12:00

Community

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answered Jun 17 '16 at 21:43

David Thomas

778
5
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You're assuming C++ not C. Is there a difference? – RamblinRose Jun 18 '16 at 04:31
1

ANSI C99 will initialize auto scope (function scope, non-static, non-thread-local) variables to an "indeterminate" value (garbage) in the absence of an initializer expression. Reference [ISO/IEC 9899:TC3](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf) See section 6.7.8 paragraph 10. _If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate._ – David Thomas Jun 21 '16 at 18:48

score 1 · Answer 2 · answered Jun 17 '16 at 21:29

1

Your Debug build may be setting count to 0 due to the nature of that build configuration but not in Release build. You need to initialize count to zero. Always initialize variables.

answered Jun 17 '16 at 21:29

RamblinRose

4,883
2
21
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size_t different default value when running through VS2013 debugger vs CommandLine

2 Answers2