If you build a program using floating-point arithmetic with DJGPP and then try to run it on a box without a FPU (such as the 386, or 486SX), the program will die at the first attemt to use the floats.
The solution for this is to tell DJGPP to use floating point emulation.
While there is the -msoft-float GCC option, which seems to be recognized in the DJGPP port too, the option does not work under DJGPP.
There is a DJGPP FAQ item about FPU emulation. It turns out the easiest way is to just add -lemu to linker options.
Also, if you target the 386, add -march=i386 to compiler options. Otherwise the program might crash, as DJGPP can use an instruction that is not supported on the 386. (Not sure about 486. Is Pentium is the default target? Or the 486? Either way, it is good practice to specify -march as the lowest CPU the app needs to run on.)