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Full Discussion: Why does this example C code run and yet SHOULD either not compile or give a segmentation fault?
Top Forums Programming Why does this example C code run and yet SHOULD either not compile or give a segmentation fault? Post 303032978 by jim mcnamara on Wednesday 27th of March 2019 06:33:32 PM
Old 03-27-2019
This is basically another way to do the undefined operation thing.

asm:
Not part of standard C, so whatever asm does is implementation defined, i.e., the people who wrote gcc
Since it's not mentioned in ISO C standard (n1570 draft-- C2011), but mentioned in annex J (common extensions):

Quote:
J.5.10 The asm keyword

1 The asm keyword may be used to insert assembly language directly into the translator output (6.8). The most common implementation is via a statement of the form:

asm ( character-string-literal );
Annex J is informative, not normative, so an implementation need not provide inline assembly, and if it does it's not prescribed in which form. But it's a widespread extension, though not portable since compilers do indeed implement it differently.

In the C++ standard (n3376 draft of the C++11 standard), it is NOT mentioned in the body of the standard.

Quote:
7.4 The asm declaration [dcl.asm]

1 An asm declaration has the form

asm-definition:

asm ( string-literal ) ;

The asm declaration is conditionally-supported; its meaning is implementation-defined. [ Note: Typically it is used to pass information through the implementation to an assembler. - end note ]
I think Rudi correct. Try using return statements. That return values used by the calling code. Other than learning what not to do for reasonable code, what does this do for you? If you had not asked here your might have accidentally created a horrible bug in a piece of code that you thought was okay. It's okay with me, but it does not seem all that helpful....
Last edited by jim mcnamara; 03-28-2019 at 12:06 PM..
This User Gave Thanks to jim mcnamara For This Post:
wisecracker
 

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LEARN ABOUT DEBIAN

z88dk

z88dk(1)							z88 Development Kit							  z88dk(1)

NAME

       z88dk - The z88 Development Kit.

DESCRIPTION

       The  z88  Development  Kit (hereafter known as z88dk) is an advanced set of tools allowing the production of complex programs for z80 based
       computers in either C or assembly language.  The name z88dk originates from the time when the project was founded and  targetted  only  the
       Cambridge z88 portable.

       The  compiler  featured in z88dk is much enhanced Small C compiler, the compiler accepts many features of ANSI C and is only deficient in a
       few areas where implementation on a z80 processor might prove inefficient. The compiler performs simple optimizations, but the bulk of  the
       optimization is done by a set of peep-hole rules, which will typically reduce the size of a large project by up to a third.

	      The  libraries  supplied with z88dk are designed to be as generic as possible, indeed it is possible to port to a new machine simply
	      by supplying two library routines and some startup code. It is hoped that one day z88dk will support as many z80 based  machines	as
	      there is information available and sufficient interest in.

	      z88dk contains usable tools:

	      o  zcc - the frontend of z88dk is called zcc, it is this that you should call if you want to do any compilations.

	      o  z80asm - Z80 assembler compiler

	      o  copt - Z80 asm optimizer code

	      o  appmake - produce files which are suitable for use in emulators or on the real hardware

	      o  sccz80 - Small-C/Plus compiler

SEE ALSO

       z88dk(1), z88dk-zcc(1), z88dk-z80asm(1), z88dk-appmake(1), z88dk-copt(1).

AUTHOR

       z88dk  was  written  by	Dominic  Morris <dom@z88dk.org>, and others.  This manual page was written by Krystian Wlosek <tygrys@waw.pdi.net>
       using exists documentation, for the Debian GNU/Linux system.

								 01 December 2009							  z88dk(1)
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