c program

Re: c program

In message
<11fc6b6d-2276-45e0-9d53-bca2d0e04995@j3 3g2000pri.googl egroups.com>,
smarty <csmgsarma@gmai l.comwrites

>On May 10, 4:19 pm, sulekhaswe...@g mail.com wrote:

>Hi,
>>
>can any one give a brief outline of the different stages in the
>execution of a C program , in terms of compilation, pre-processing,
>linking etc

>
>1.the file u create in editor is saved as ".c" file
>2. this '.s' file is then PREPROCESSED for compilation .
>3. the preprocessed file undergoes compilation to generate a
>'.asm' (assembly file) or '.s' or '.src' file.
>4. this source file is assembled to generate a '.obj' file
>5. this .obj file is combined with other '.obj' or '.lib' files to
>generate an executable file.

1 You write text (C source) in to a TEXT editor. Often the editor in an
IDE

2 You "Compile" the source.
These days this will give you an object file for linking.
Under the hood there are several steps

2.1 The pre-processor does a *textual* replacement of macros and
defines. This is why it is often required that macros have ( ) around
them when they are defined.

2.2 the now expanded text file is compiled. At one time this could be
up to THREE passes and the command "CC file.c" actually fed file.c to a
batch file called cc that called the three parts of the compiler. This
would turn our assembler code in a text file. You then needed to
assemble the text file to object code.

Modern compilers are "single pass" which means they hide all the
messing about and go from the source code text to object files in "one
pass" and do not generate assembler code. Thus a separate assembler is
not needed. In reality there is usually a pre-proccessor phase and the
compiler will generate intermediate files and tables.

These days there is more memory. In the Good old Days you use to have to
swap floppy disks for compile, assemble and link phases :-) (and 8inch
floppies at that :-))))

3 linking. This links the various program object files and the library
files

linking needs to sort out all the extern function and data calls between
modules and the library. It knits the modules together in one object
file

In some cases years ago where there is only a single file and no calls
to the library the object file from the assembler or compiler could run
without linking.

The out put from the linker can be further processed to give S-Rec,
Intel Hex or other files for downloading to eprom/flash programmers.

--
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\/\/\/\/\ Chris Hills Staffs England /\/\/\/\/
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

Re: c program

On May 10, 4:19 pm, sulekhaswe...@g mail.com wrote:

Hi,
>
can any one give a brief outline of the different stages in the
execution of a C program , in terms of compilation, pre-processing,
linking etc

1.the file u create in editor is saved as ".c" file
2. this '.s' file is then PREPROCESSED for compilation .
3. the preprocessed file undergoes compilation to generate a
'.asm' (assembly file) or '.s' or '.src' file.
4. this source file is assembled to generate a '.obj' file
5. this .obj file is combined with other '.obj' or '.lib' files to
generate an executable file.

Re: c program

sulekhasweety@g mail.com said:

Hi,
>
can any one give a brief outline of the different stages in the
execution of a C program , in terms of compilation, pre-processing,
linking etc

There are eight translation phases. They are documented in the C Standard.
Briefly, they are:

1) physical source file characters are mapped to the source character set,
and trigraph replacements happen;
2) line splicing happens;
3) source file is decomposed into pp-tokens; comments are removed (replaced
by one space character);
4) preprocessing directives are executed and macro invocations are
expanded;
5) escape sequences are converted into characters;
6) string literal concatenation occurs;
7) pp-tokens are converted to tokens, and translation (compilation, if you
like) occurs;
8) linking.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

Re: c program

sulekhasweety@g mail.com wrote:

Hi,
>
can any one give a brief outline of the different stages in the
execution of a C program , in terms of compilation, pre-processing,
linking etc

No.
A C implementation can do two different things.
It can translate a C program.
It can execute a C program.

Compilation, pre-processing, linking are related to translation.

N869

5.1.1.2 Translation phases

[#1] The precedence among the syntax rules of translation is
specified by the following phases.5)

1. Physical source file multibyte characters are mapped
to the source character set (introducing new-line
characters for end-of-line indicators) if necessary.
Trigraph sequences are replaced by corresponding
single-character internal representations .

2. Each instance of a backslash character (\) immediately
followed by a new-line character is deleted, splicing
physical source lines to form logical source lines.
If, as a result, a character sequence that matches the
syntax of a universal character name is produced, the
behavior is undefined. Only the last backslash on any
physical source line shall be eligible for being part
of such a splice. A source file that is not empty
shall end in a new-line character, which shall not be
immediately preceded by a backslash character before
any such splicing takes place.

3. The source file is decomposed into preprocessing
tokens6) and sequences of white-space characters
(including comments). A source file shall not end in
a partial preprocessing token or in a partial comment.
Each comment is replaced by one space character. New-
line characters are retained. Whether each nonempty
sequence of white-space characters other than new-line
is retained or replaced by one space character is
implementation-defined.

4. Preprocessing directives are executed, macro
invocations are expanded, and _Pragma unary operator
expressions are executed. If a character sequence
that matches the syntax of a universal character name
is produced by token concatenation (6.10.3.3), the
behavior is undefined. A #include preprocessing
directive causes the named header or source file to be
processed from phase 1 through phase 4, recursively.
All preprocessing directives are then deleted.

5. Each source character set member and escape sequence |
in character constants and string literals is
converted to the corresponding member of the execution
character set; if there is no corresponding member, it
is converted to an implementation-defined member.

6. Adjacent string literal tokens are concatenated.

7. White-space characters separating tokens are no longer
significant. Each preprocessing token is converted
into a token. The resulting tokens are syntactically
and semantically analyzed and translated as a
translation unit.

8. All external object and function references are
resolved. Library components are linked to satisfy
external references to functions and objects not
defined in the current translation. All such
translator output is collected into a program image
which contains information needed for execution in its
execution environment.


--
pete

Hi,

can any one give a brief outline of the different stages in the
execution of a C program , in terms of compilation, pre-processing,
linking etc