CODEWITHSUNDEEP
visual-studio-2010visual-c++
vico
vico

Reputation: 18171

Garbage in debug

I found strange Visual Studio 2010 behavior while debugging project. Variable string s was initialized with "", but debugger shows garbage. Debug point is in the second line of s initialization.

enter image description here

if I do cout<<s, it prints normal value - not garbage.

One more immage to be shure where is breakpoint enter image description here

In other project places debugger works fine. Procedure where I have garbage is win message handler. Message was transmitted from same project other thread.

LRESULT CMainWindow::OnMessageAuthorise(WPARAM wParam, LPARAM lParam)
{
string s= ""; 
...
}

What is wron?

UPD: Problem is in profile Debug/Release selection. If I choose Release I have these garbage on variables. Why it is so?

Upvotes: 0

Views: 579

Answers (1)

Ofek Shilon
Ofek Shilon

Reputation: 16147

Short answer: unless you're willing to inspect disassembly, you can't set watches in release builds. That's what debug builds are for.

Longer answer: In release builds many optimizations can make the mapping of a variable name to a memory address much harder. The simplest case - the variable might have no memory address: it can be saved only in registers. Traditional generation of PDB files (the files that hold - among others - this mapping info) didn't even try to cope with the difficulties emanating from optimizations, but since VS2012 a new switch takes a substantial step in that direction.

Upvotes: 1

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