short_call_convention patch from tcc bugzilla
BUGZILLA:
interfacing with other compilers
extend the return value to the whole register if necessary.
visual studio and gcc do not always set the whole eax register
when assigning the return value of a function.
We've encountered wrong execution results on i386 platforms with an
application that uses both code compiled with TCC and code compiled
with other compilers (namely: Visual Studio on Windows, and GCC on
Linux).
When calling a function that returns an integer value shorter than 32
bits, TCC reads the return value from the whole EAX register,
although the code generated by the other compilers can only sets AL
for 8 bit values or AX for 16 bits values, and the rest of EAX can be
anything.
We worked around this with the attached patch on i386 for the version
0.9.26, but we did not look at other platforms to find if there are
similar issues.