CODEWITHSUNDEEP
dllfloating-pointc++builder
Mathew Joy
Mathew Joy

Reputation: 121

Invalid floating point operation while loading dll

I got a problem recently that when I added a code to a lib, which is used by a dll, the dll cannot be loaded. I get an exception "Floating point invalid operation at xxx". When I comment out the code it works. The code added is just straight forward like creating a TADOQuery object, add the sql statment and the parameters, then do an open, check value etc. Nothing suspicious. Now when I uncomment the code and comment another chuck of code in the unit elsewhere, it starts to work. So obviously the newly added code was just tripping the issue caused elsewhere.

Now this error happens when LoadLibrary() call is invoked. There is no attach code. The DllMain, just has a return 1. When this happens the assembly code is always at FSTP tbyte ptr doing a System::Variant::Clear().

Anyone has come across such issues? Any tips on how to debug is also appreciated.

PS: It could also be Embarcadero's compiler issue. I recently figured out that the assembly generated for a combination of assignment and comparison is incorrect. The only suspicion here is the lib that the dll uses is large. When I do a clean and build of the lib, the total lines shows 5.7m. Maybe there is some setting for large libs?

IDE-XE4, c++ builder OS-Win 7

Thanks, Mathew Joy

Upvotes: 2

Views: 1182

Answers (1)

Rudy Velthuis
Rudy Velthuis

Reputation: 28836

C++Builder and Delphi have different default FPU settings than, say, MSVC and the DLLs written in it.

It probably goes like this: After DllMain, certain exceptions are masked to be hidden. But before the first floating point operation in C++Builder code occurs, that exception is unmasked and the exception occurs.

This is a known problem with C++Builder/Delphi floating point and DLLs.

Upvotes: 2

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