TyRoXx

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About TyRoXx

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  1. The interpreter does not detect this operand pair as problematic before executing a division or modulo: int int_min = -2147483648; int neg_one = -1; int never_computed = (int_min / neg_one); int the_same_error = (int_min % neg_one); The above AS code crashes with a system error like "floating point exception" on GNU/Linux x86. The C++ signed division is usually compiled to an idiv instruction on x86. The idiv instruction raises an error when trying to divide -2147483648 by -1 resulting in a crash of the AngelScript host application. This is a common error in C and C++ code. People check for division by zero but are not aware of the described problem. The same is true for modulo % (asBC_MODi) which also uses idiv. The implementation of asBC_DIVi is lacking a check for -2147483648 / -1: (Revision 1583, sdk/angelscript/source/as_context.cpp:2924) case asBC_DIVi: { int divider = *(int*)(l_fp - asBC_SWORDARG2(l_bc)); if( divider == 0 ) { // Need to move the values back to the context m_regs.programPointer = l_bc; m_regs.stackPointer = l_sp; m_regs.stackFramePointer = l_fp; // Raise exception SetInternalException(TXT_DIVIDE_BY_ZERO); return; } *(int*)(l_fp - asBC_SWORDARG0(l_bc)) = *(int*)(l_fp - asBC_SWORDARG1(l_bc)) / divider; } l_bc += 2; break; AngelScript should raise an exception before trying to divide -2147483648 by -1 like it does on division by zero. The implementations of asBC_DIVi and asBC_MODi have to be extended to cover this case. If AngelScript does constant folding, the problem may be present in there, too.