is this possible

Then you would have a build system ... that builds the three variants
I have that already.

Hans-Bernhard,

The build works just fine, there is no problem there, if you understand this to be a build problem, this thread must have gone astray.

as I started the thread "It happens that I am looking at the type b code trying to figure out something in type a (the codes are VERY similar)."

What I hoped for was a source file where it was crystal clear for every line which build it belonged to.

This thread was originated because I made some changes in a ~200 line segment for type q which should have been inserted in the ~200 line segment for type x.

I recovered without any problems, just it would be nice not to repeat.

Now that I iunderstand that you are talking 'build' wher I am reading 'edit' it becomes obvious why I have misunderstood you.

Erik

Then you would have a build system ... that builds the three variants
I have that already.

Hans-Bernhard,

The build works just fine, there is no problem there, if you understand this to be a build problem, this thread must have gone astray.

as I started the thread "It happens that I am looking at the type b code trying to figure out something in type a (the codes are VERY similar)."

What I hoped for was a source file where it was crystal clear for every line which build it belonged to.

This thread was originated because I made some changes in a ~200 line segment for type q which should have been inserted in the ~200 line segment for type x.

I recovered without any problems, just it would be nice not to repeat.

Now that I iunderstand that you are talking 'build' wher I am reading 'edit' it becomes obvious why I have misunderstood you.

Erik

The build works just fine, there is no problem there, if you understand this to be a build problem, this thread must have gone astray.

It went astray when you failed to notice that changes to the build system are exactly what it takes to solve your authoring confusion. You want to modify the syntax of the file you edit, to make more explicit which variant each line of that file belongs to. So far, so good. But the you want to do that, this file would be incompatible with C source file structure. So it has to be input to something else than the C compiler: a preprocessor is needed. That's exactly what I proposed 'sed' for: it can handle the file structure you want, and turn it into compilable C.

This thread was originated because I made some changes in a ~200 line segment for type q which should have been inserted in the ~200 line segment for type x.

In this particular case, I really can't see why you want to keep all these variants in one file --- 200 lines is well worth starting a new file. This would be a lot easier by putting these segments into separate files, and then in the main file just writing

#if defined(VARIANT_A)
# include "fragment_foo_A.c"
#elif defined(VARIANT_B)
# include "fragment_foo_B.c"
#elif defined(VARIANT_C)
# include "fragment_foo_C.c"
#endif

"This would be a lot easier by putting these segments into separate files, and then in the main file just writing ..."

And for #include, the preprocessing tokens after include in the directive are processed just as in normal text (i.e., subject to macro replacement), so one can locate all the names in the source file's front matter or separate header file, leaving the code in the function's body relatively clean and free of #if/#elif/#else/#endif if that's desireable.

#if defined(VARIANT_A)
# define FRAGMENT_FOO1  "fragment_foo1_A.c"
# define FRAGMENT_FOO2  "fragment_foo2_A.c"
# define FRAGMENT_FOO3  "fragment_foo3_A.c"
#elif defined(VARIANT_B)
# define FRAGMENT_FOO1  "fragment_foo1_B.c"
# define FRAGMENT_FOO2  "fragment_foo2_B.c"
# define FRAGMENT_FOO3  "fragment_foo3_B.c"
#elif defined(VARIANT_C)
# define FRAGMENT_FOO1  "fragment_foo1_C.c"
# define FRAGMENT_FOO2  "fragment_foo2_C.c"
# define FRAGMENT_FOO3  "fragment_foo3_C.c"
#endif

void foo(void)
{
    #include FRAGMENT_FOO1
    /*
     * ... some code ...
     */
    #include FRAGMENT_FOO2
    /*
     * ... some more code ...
     */
    #include FRAGMENT_FOO3
}

In this particular case, I really can't see why you want to keep all these variants in one file --- 200 lines is well worth starting a new file. This would be a lot easier by putting these segments into separate files, and then in the main file just writing

#if defined(VARIANT_A)
# include "fragment_foo_A.c"

Anyhow, Hans-Bernhard, I do appreaciate your efforts, believe me. However I was looking for a simple solution to something that happens about once or twice a year.

As to the #include, I do that by a switch in the ,bat file like this fragemet show

IF "%1"=="b" goto lcb
IF "%1"=="ba" goto lcba
......

:lcb
copy ..\ss\usmainb.c usmain.c >..\trash\trashbin
copy ..\ss\usledst1.c usledstb.c >..\trash\trashbin
copy ..\ss\ussgndv1.c ussgndvr.c >..\trash\trashbin
goto lxx

Again, I apprecieate your efforts and am sure that your solutions work, but none accomplish the original desire of a simple solution, not to a problem, but to an annoyance.

Lets us stop here

Erik