• Sean Kelly (38/38) Aug 01 2005 By disassembling some test code, it's clear that inout parameters are ju...

Sean Kelly <sean f4.ca> writes:

By disassembling some test code, it's clear that inout parameters are just
pointers that are implicitly dereferenced when needed.  And treating them as
pointers using inline asm works just fine.  But the assembler seems to have
problems referencing inout parameters < 32 bits in asm blocks.  Here's some
sample code:

# version( test1 )
# {
#     byte fn( inout byte val )
#     {
#         asm
#         {
#             mov EAX, val;
#             mov AL, [EAX];
#         }
#     }
# }
# 
# byte nonasm( inout byte val )
# {
#     return val;
# }
# 
# void main()
# {
#     byte b;
#     nonasm( b );
# }

C:\code\d>dmd test -version=test1
test.d(7): bad type/size of operands 'mov'

If I compile without the version flag and inspect the code however, I see:

# _D5test16nonasmFKgZg    comdat
#         assume  CS:_D5test16nonasmFKgZg
#                 mov     AL,[EAX]
#                 ret

so I'm obviously doing the right thing.  I know I could get around this by
making the block naked or by using pure asm to reference the variable, but this
should not be necessary.


Sean