Translate from c to asm

[Ronny Mandal]

Hello!

Can anyone please provide me some resources, or maybe an algorithm / tip on
translating from c to assembler (arbitrary assembler, but LC2 is preferred.
The c-routines themselves are small, trivial ones). I hvae an exam in a
computer science course in 4 days, and I simply cannot get a grip on this
topic.

Any help would be highly appreciated.


Regards,

Ronny Mandal

 

[mhandis]

Try GCC's -S argument:

gcc -S test.c

This should create an assembly version called test.s.

 

[Thomas Matthews]

Hello!

Can anyone please provide me some resources, or maybe an algorithm / tip on
translating from c to assembler (arbitrary assembler, but LC2 is preferred.
The c-routines themselves are small, trivial ones). I hvae an exam in a
computer science course in 4 days, and I simply cannot get a grip on this
topic.

Any help would be highly appreciated.


Regards,

Ronny Mandal

Check you compiler documentation. Many have an option for creating
assembly language listings. Also check your debugger documentation.
Some debugger's have this capability too. You may want to see if
they have "interwoven" capability, which is to print a C language
statement, then followed by the assembly language. This would
be very helpful since you can see what assembly language was created
for each C statement.

--
Thomas Matthews

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Other sites:
http://www.josuttis.com -- C++ STL Library book
http://www.sgi.com/tech/stl -- Standard Template Library

 

[nrk]

Try GCC's -S argument:

gcc -S test.c

This should create an assembly version called test.s.

On a related and totally off-topic note, does anyone have a good,
comprehensive, online reference for the AT&T assembler syntax? I've tried
to find one, and always come up short.

-nrk.

 

[CBFalconer]

Can anyone please provide me some resources, or maybe an algorithm
/ tip on translating from c to assembler (arbitrary assembler, but
LC2 is preferred. The c-routines themselves are small, trivial
ones). I hvae an exam in a computer science course in 4 days, and
I simply cannot get a grip on this topic.

All you have to do is be able to code in assembly. The normal way
of performing the transformation is via a compiler whose output
phase was designed by someone so capable, but hand compilation is
also acceptable. In any case you have to understand the
destination machine.

I suspect you are going to fail.

 

[Irrwahn Grausewitz]

On a related and totally off-topic note, does anyone have a good,
comprehensive, online reference for the AT&T assembler syntax? I've tried
to find one, and always come up short.

[still way OT:]

I had the same problem, but found out that you can make gcc
generate Intel syntax assembler:

gcc -S -masm=intel test.c

Regards

 

[Nejat AYDIN]

mhandis wrote: [...]
On a related and totally off-topic note, does anyone have a good,
comprehensive, online reference for the AT&T assembler syntax? I've tried
to find one, and always come up short.

Did you try "man as", or online GNU documentation such as,
http://www.gnu.org/software/binutils/manual/gas-2.9.1/html_chapter/as_toc.html

http://www.gnu.org/software/binutils/manual/gas-2.9.1/html_chapter/as_16.html#SEC196

 

[Kevin Goodsell]

Hello!

Can anyone please provide me some resources, or maybe an algorithm / tip on
translating from c to assembler (arbitrary assembler, but LC2 is preferred.
The c-routines themselves are small, trivial ones). I hvae an exam in a
computer science course in 4 days, and I simply cannot get a grip on this
topic.

Translating C to an assembler is very unlikely to be possible in most
cases. The only way you could get an assembler out of a C source is if
that source happens to be the source for an assembler. If I take the
source for a C "hello world" program, about the only thing it can be
translated into is a "hello world" program (usually either in machine
language or assembly language). It can't be translated into an assembler
any more than it could be translated into an editor or a compiler - the
logic just isn't there.

-Kevin

 

[Ronny Mandal]

All you have to do is be able to code in assembly. The normal way
of performing the transformation is via a compiler whose output
phase was designed by someone so capable, but hand compilation is
also acceptable. In any case you have to understand the
destination machine.

I suspect you are going to fail.

I think you're almost right. But it is approx. 4 days remaining, so a little
intensivereading won't hurt.
The programs that are to be translated are only like "Hello World, etc",
hence the chances are good indeed!

RM

 

[Anuj Heer]

Actually there are disassemblers available on the internet which can
convert full exe codes back into assembly language. You can also find
decompilers which can convert EXE files back to C codes. But these
programs come with a lot of extra overhead as they convert the whole
code on a as is where is basis to the end code and will make your life
hell trying just to figure out where the actual usable code segment
is. Studying hard can solve the problem in just one night. But if you
still want those just mail me asap at (e-mail address removed).

anuj

 

[CBFalconer]

I think you're almost right. But it is approx. 4 days remaining, so
a little intensivereading won't hurt.
The programs that are to be translated are only like "Hello World,
etc", hence the chances are good indeed!

Then simplify the problem. Assume you have a puts subroutine
available, and all the program has to do is supply it the
appropriate parameters, and then return a status. So you have to
look up how to pass parameters, how to call a subroutine, and how
to exit a routine with a value. You can simplify parameter
passing to pushing onto a stack on most systems, don't know about
yours. Others require using registers.

You should have done all this months ago.

 

[David M. Wilson]

Actually there are disassemblers available on the internet which can
convert full exe codes back into assembly language

Hey there!

You don't need to jump the gun that far.. I think most compilers have
an assembly intermediate stage. This is definately true of gcc and
Turbo C.

To the OP: the assembly code generated by a compiler can tend to be
distinguishable from hand-written assembly. There is a fairly good
chance that if you try to hand in compiler-generated assembly, you
will be caught out. Stripping out the comments will not do.

It is not impossible to pick up a good bit of asm in a couple of days
if you really put your mind to it.


David.

 

[Anuj Heer]

Hey there!

You don't need to jump the gun that far.. I think most compilers have
an assembly intermediate stage. This is definately true of gcc and
Turbo C.

agreed totally!!!

To the OP: the assembly code generated by a compiler can tend to be
distinguishable from hand-written assembly. There is a fairly good
chance that if you try to hand in compiler-generated assembly, you
will be caught out. Stripping out the comments will not do.

yes, examiners who have been at it for quite some time can smell such
code from miles away.

It is not impossible to pick up a good bit of asm in a couple of days
if you really put your mind to it.


David.

that as everyone has said already would be the best approach unless
you don't like programming which will make it the most difficult task
of your life

anuj
(e-mail address removed)

 

[Mac]

Translating C to an assembler is very unlikely to be possible in most
cases. The only way you could get an assembler out of a C source is if
that source happens to be the source for an assembler. If I take the
source for a C "hello world" program, about the only thing it can be
translated into is a "hello world" program (usually either in machine
language or assembly language). It can't be translated into an assembler
any more than it could be translated into an editor or a compiler - the
logic just isn't there.

-Kevin

You are trying awfully hard to be pedantic, but the usage of the term
"assembler" to mean "assembly language" is quite widespread. If you want
to assert that it is unambiguously wrong, I think you have to quote an
authoritative source of some sort.

Mac

 

[Kevin Goodsell]

On Sun, 07 Dec 2003 19:39:37 +0000, Kevin Goodsell wrote:

You are trying awfully hard to be pedantic, but the usage of the term
"assembler" to mean "assembly language" is quite widespread.

Oh, is /that/ what he meant?

-Kevin

 

[Ken Asbury]

Translating C to an assembler is very unlikely to be possible in most
cases. The only way you could get an assembler out of a C source is if
that source happens to be the source for an assembler. If I take the
source for a C "hello world" program, about the only thing it can be
translated into is a "hello world" program (usually either in machine
language or assembly language). It can't be translated into an assembler
any more than it could be translated into an editor or a compiler - the
logic just isn't there.

-Kevin

Hmmm...

In every IDE I've seen (not an exhaustive list but certainly
representative) one can set the simulator/emulator window to
display C (C++) interspersed with assembly. Tag-and-drag to
whatever editor is available, comment out the C, edit out the
extraneous fields of line numbers and machine code, change the
compiler-provided names to something that the assembler will
eat and, VOILA, you have a thorough understanding of how the
compiler works and a decent head-start on learning the specific
assembly language of the selected micro.

Realizing that this does not meet the OP's timeline or, perhaps,
LC2 requirement (too lazy to google) it still provides the
foundation for making an excellent living.

Regards,
Ken Asbury

 

[nrk]

mhandis wrote: [...]
On a related and totally off-topic note, does anyone have a good,
comprehensive, online reference for the AT&T assembler syntax? I've
tried to find one, and always come up short.

Did you try "man as", or online GNU documentation such as,
http://www.gnu.org/software/binutils/manual/gas-2.9.1/html_chapter/as_toc.html

http://www.gnu.org/software/binutils/manual/gas-2.9.1/html_chapter/as_16.html#SEC196

Thanks, I have perused them in the past (indeed, that's the only way I could
make any sense out of AT&T style asm generated by gcc by default).
However, I've always wondered if that is the best and comprehensive
reference of the AT&T syntax... certainly the best I've managed to find
(barring a few djgpp related web pages) in the past.

-nrk.

 

[nrk]

On a related and totally off-topic note, does anyone have a good,
comprehensive, online reference for the AT&T assembler syntax? I've
tried to find one, and always come up short.

[still way OT:]

I had the same problem, but found out that you can make gcc
generate Intel syntax assembler:

gcc -S -masm=intel test.c

Regards

Duh!! Never even occurred to me that gcc could be asked to generate
assembler output in a different dialect (go on, I know how dumb I am)!!

Now, this is good for me (confession time: I prefer the Intel syntax as I am
more comfortable with it, and AT&T's switch of source, destination was hard
to cope with).

Thank you,
-nrk.