These are real questions that I wonder about. If you don't want to answer, leave it to someone else.

Question 2: Another minor issue for me is when I am coding in MS COFF mode and I want to compile COFF objects. I want to be able to use the extended features of fasm (.if, .then) and all the layers that it offers, but it seems to be including all the API functions too when I include the win32ax include file, is this too much to include for a simple coff project? Should I include that file for simple coff projects?

Question 3: Can I reference structures with pointer to structures in the procedure argument? How?

struc xyz ... {<stuff>}
the_struc xyz ...
stdcall function, the_struc, ...    

Question 4 (A very bothersome issue for me): In NASM, I can simply switch to the data segment by issuing a macro [SECTION] to switch to the data section and I can declare data anywhere in source code and it will be put into the active section. How can I declare data in the data section without adding it directly to the data section manually? This problem is one of the problems that caused me to abandon fasm, I couldn't find an easy way to live with this.

Question 5: The fixup section, should I include it in every new project? What exactly should I put in it? This bothers me quite a bit, an explanation would be appreciated.

Question 6: In NASM I provide the -e command line option to see the output from macros, how can I do that in fasm to see what my macros produce?

Question 7: How can I make a section shared, using fasm? The fasm manual does not specify or support all the flags that I need to use.

section directive defines a new section, it should be followed by quoted string defining the name of section, then one or more section flags can follow. Available flags are: code, data, readable, writeable, executable, shareable, discardable, notpageable.

Question 8: How does fasm treat data declared as .bss and .data, are there any merging going on?

Question 9: I have some fasm source files made by someone else and they use 'on nul' on top of the source file, what does this do?

Question 10: How can I customize the prologue and epilogue of my proc without interfering with the rest of the proc endp structure?

Question 12: Does fasm have mechanisms for using SEH or do I have to create a macro myself?

Question 13: How can I detect the target architecture, in other assemblers you can restrict it by issuing a .386 directive, and so on, but in fasm I don't know how to detect the final architecture without going through all the instructions manually.

Question 14: How can i temporarily disable fasm's optimization?

Question 15: How can I align the stack when I use proc and endp?

Question 16: (Not very relevant): How can I customize the dos stub from fasm?

Question 17: How can I specify the executable base address or use the fixed base address option?

Question 18: The include files in fasm has removed the conditional testing for different versions of windows, are there any flags I can set so the include files works for a specific windows version?

Question 19: Fasm ships with wsock32 which is deprecated and is a stub for ws32, are there plans to include the most up to date winsock include file?

mov eax, 10
section .data
align 16
  _tea db 'A cup of tea',0
section .code
mov ecx, 20
    

; example of making Win32 COFF object file

format MS COFF

extrn '__imp__MessageBoxA@16' as MessageBox:dword

section '.text' code readable executable

 public _demo

 _demo:
        push    0
section '.data' data readable writeable
        _tea db 'A cup of tea',0
section '.text' code readable executable
        push    _caption
        push    _message
        push    0
        call    [MessageBox]
        ret

section '.data' data readable writeable

 _caption db 'Win32 assembly',0
 _message db 'Coffee time!',0    

By default section is aligned to double word (four bytes), in case of Microsoft COFF variant other alignment can be specified by providing the align operator followed by alignment value (any power of two up to 8192) among the section flags.

assert x or 1 ;check if x is defined only once
x=1    

flat assembler version 1.71.39 (3145344 kilobytes memory)
2 passes, 0 bytes.

assert x or 1 ;check if x is defined only once
x=1
x=2 ;redefine x    

flat assembler version 1.71.39 (3145344 kilobytes memory)
test.asm [1]:
assert x or 1
error: symbol 'x' out of scope.

The only way that I am aware of generating an error (not a warning) when a variable is redefined would be with the assembler equals (=) assignment.