Partly recompilation generates invalid address fault?

[superfury]

I'm making an x86 emulator with C++ (currently 8086/80186 with some little unfound errors). When I'm compiling all the files (deleting all *.o files and running make), the emulator runs fine (still some errors, but it runs). When I run make, just having one file adjusted, the emulator (JPCSP, a PSP emulator) gives me an invalid opcode/address fault. The emulator does use some pointers at different places though (mostly dynamic memory and optimization), can this be the cause? Causing addressing errors with partial recompilation using make?

[ne555]

undefined behaviour is undefined.
That's the best guess with the information provided.

> dynamic memory and optimization
encapsulate your memory management (by instance std::vector)
don't preoptimize.