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flat assembler > Windows > The best start to a Windows program

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Furs



Joined: 04 Mar 2016
Posts: 1155


fasmnewbie wrote:
C is not a "Windows" program. It's a high-level language that should appear / behave the same across platforms. Whatever happens behind the scene should not be of concern to users / programmers because they are platform-specific by then. It's the same with C's exit sequence. Whatever happens past the RET is ignorable.

Oh, you're perfectly right but I was thinking of the thread's title when I read your post, didn't realize you were talking about C itself.
Post 08 May 2018, 12:18
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fasmnewbie



Joined: 01 Mar 2011
Posts: 512


Furs wrote:

fasmnewbie wrote:
C is not a "Windows" program. It's a high-level language that should appear / behave the same across platforms. Whatever happens behind the scene should not be of concern to users / programmers because they are platform-specific by then. It's the same with C's exit sequence. Whatever happens past the RET is ignorable.

Oh, you're perfectly right but I was thinking of the thread's title when I read your post, didn't realize you were talking about C itself.



It works either way. From C to binary, main should be the startup function. OTOH, if you're approaching C from the bottom up, C expects similar startup structure, if you're producing an executable. "main" as the startup function is defined in C99 Specification:

Code:
5.1.2.2.1 Program startup
The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int and with no parameters:

int main(void) { /* ... */ }


It is also defined in C++98 Standard

Code:
3.6.1 Main function [basic.start.main]
1 A program shall contain a global function called mainwhich is the designated start of the program. [...]

2 An implementation shall not predefine the main function. This function shall not be overloaded. It shall have a return type of type intbut otherwise its type is implementation defined. All implementations shall allow both of the following definitions of main:

int main() { /* ... */ }
and

int main(int argccharargv[]) { /* ... */ }


So in hosted environment, as in Windows and Linux, main is a special function assuming these special feature;

1. Global
2. Non-reentrant
3. Not overloaded
4. Should be able to take arguments (from the command lines)
5. Static, as in case of JAVA

My low-level examples here will not work without main as the startup module for both Linux and Windows. Or at least I have to go through non-conventional techniques (re-naming the startup point etc) to produce similar result.

If you're using C in a freestanding environment, then you are free to come up with your own startup function.
Post 08 May 2018, 19:41
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Melissa



Joined: 12 Apr 2012
Posts: 55

I think that in C, main can be recursively called, while in C++ cannot. Can't remember exactly.
Post 09 May 2018, 02:50
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 15791
Location: Misner space


Melissa wrote:
I think that in C, main can be recursively called ...

This code would seem to support that:

Code:
main(t,_,a)
char *a;
{return!0<t?t<3?main(-79,-13,a+main(-87,1-_,
main(-860a+1 )+a)):1,t<_?main(t+1_a ):3,main ( -94, -27+ta
)&&t == 2 ?_<13 ?main ( 2_+1"%s %d %d\n" ):9:16:t<0?t<-72?main(_,
t,"@n'+,#'/*{}w+/w#cdnr/+,{}r/*de}+,/*{*+,/w{%+,/w#q#n+,/#{l,+,/n{n+\
,/+#n+,/#;#q#n+,/+k#;*+,/'r :'d*'3,}{w+K w'K:'+}e#';dq#'l q#'+d'K#!/\
+k#;q#'r}eKK#}w'r}eKK{nl]'/#;#q#n'){)#}w'){){nl]'/+#n';d}rw' i;# ){n\
l]!/n{n#'; r{#w'r nc{nl]'/#{l,+'K {rw' iK{;[{nl]'/w#q#\
n'wk nw' iwk{KK{nl]!/w{%'l##w#' i; :{nl]'/*{q#'ld;r'}{nlwb!/*de}'c \
;;{nl'-{}rw]'/+,}##'*}#nc,',#nw]'/+kd'+e}+;\
#'rdq#w! nr'') }+}{rl#'{n' ')# }'+}##(!!/")
:t<-50?_==*a ?putchar(a[31]):main(-65,_,a+1):main((*a == '/')+t,_,a\
+1 ):0<t?main ( 22 , "%s"):*a=='/'||main(0,main(-61,*a"!ek;dc \
i@bK'(q)-[w]*%n+r3#l,{}:\nuwloca-O;m .vpbks,fxntdCeghiry"),a+1);}


Compile it and see what you get. It is a good example of how awesomely clear and understandable C code can be. Wink
Post 09 May 2018, 02:53
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Melissa



Joined: 12 Apr 2012
Posts: 55

Beautiful Wink This is art!
Post 09 May 2018, 03:03
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fasmnewbie



Joined: 01 Mar 2011
Posts: 512


revolution wrote:

Melissa wrote:
I think that in C, main can be recursively called ...

This code would seem to support that:

Code:
main(t,_,a)
char *a;
{return!0<t?t<3?main(-79,-13,a+main(-87,1-_,
main(-860a+1 )+a)):1,t<_?main(t+1_a ):3,main ( -94, -27+ta
)&&t == 2 ?_<13 ?main ( 2_+1"%s %d %d\n" ):9:16:t<0?t<-72?main(_,
t,"@n'+,#'/*{}w+/w#cdnr/+,{}r/*de}+,/*{*+,/w{%+,/w#q#n+,/#{l,+,/n{n+\
,/+#n+,/#;#q#n+,/+k#;*+,/'r :'d*'3,}{w+K w'K:'+}e#';dq#'l q#'+d'K#!/\
+k#;q#'r}eKK#}w'r}eKK{nl]'/#;#q#n'){)#}w'){){nl]'/+#n';d}rw' i;# ){n\
l]!/n{n#'; r{#w'r nc{nl]'/#{l,+'K {rw' iK{;[{nl]'/w#q#\
n'wk nw' iwk{KK{nl]!/w{%'l##w#' i; :{nl]'/*{q#'ld;r'}{nlwb!/*de}'c \
;;{nl'-{}rw]'/+,}##'*}#nc,',#nw]'/+kd'+e}+;\
#'rdq#w! nr'') }+}{rl#'{n' ')# }'+}##(!!/")
:t<-50?_==*a ?putchar(a[31]):main(-65,_,a+1):main((*a == '/')+t,_,a\
+1 ):0<t?main ( 22 , "%s"):*a=='/'||main(0,main(-61,*a"!ek;dc \
i@bK'(q)-[w]*%n+r3#l,{}:\nuwloca-O;m .vpbks,fxntdCeghiry"),a+1);}


Compile it and see what you get. It is a good example of how awesomely clear and understandable C code can be. Wink



I guess thats what makes C a powerful language then. Everybody seems to be able to break anything out of it.
Post 09 May 2018, 07:12
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rugxulo



Joined: 09 Aug 2005
Posts: 2279
Location: Usono (aka, USA)

C was intentionally parsimonious. Most of the dirty tricks usually come from the preprocessor. This particular excerpt is probably some IOCCC winner from years past. EDIT: Seems sources to latest 2018 IOCCC winners were just published a few days ago.
Post 09 May 2018, 07:50
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