lib/commonio.c: Rename structure members that look like libc APIs

[alejandro-colomar]

libc is allowed to provide any functions as macros (7.1.4p1 in C23).

This means that libc is allowed to provide a free(3) macro, which could look like

#define free(p)  __free(p)

And that would be expanded by the preprocessor in our code, turning our structure members into some code that won't work (or even worse, it might misbehave).

So, fix this undefined behavior.

---

Revisions:

v1b

• Rebase

$ git rd 
1:  9bd4846f = 1:  40c6de86 lib/commonio.c: Parenthesize calls that look like libc APIs

v1c

• Rebase

$ git rd 
1:  40c6de86 = 1:  cfd05116 lib/commonio.c: Parenthesize calls that look like libc APIs

v1d

• Rebase

$ git rd 
1:  cfd05116 = 1:  190be125 lib/commonio.c: Parenthesize calls that look like libc APIs

v2

• Rename members instead of adding parentheses. This is more conventional.

$ git range-diff shadow/master gh/macro macro 
1:  190be125 < -:  -------- lib/commonio.c: Parenthesize calls that look like libc APIs
-:  -------- > 1:  8e79275b lib/commonio.c: struct commonio_ops: Add prefix 'cio_' to structure members

v2b

• Tweak commit message subject.

$ git range-diff shadow/master gh/macro macro 
1:  8e79275b ! 1:  f38b58dd lib/commonio.c: struct commonio_ops: Add prefix 'cio_' to structure members
    @@ Metadata
     Author: Alejandro Colomar <alx@kernel.org>
     
      ## Commit message ##
    -    lib/commonio.c: struct commonio_ops: Add prefix 'cio_' to structure members
    +    lib/commonio.[ch]: struct commonio_ops: Add prefix 'cio_' to structure members
     
         This structure has members that are named like libc APIs.
     

v2c

• Rebase

$ git rd 
1:  f38b58dd = 1:  6b8a5d2a lib/commonio.[ch]: struct commonio_ops: Add prefix 'cio_' to structure members

[hallyn]

Does any libc do this?

[alejandro-colomar]

Does any libc do this?

I'm experimenting with an _Optional qualifier that is being debated within the C Committee.
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3422.pdf

I've installed the following header (written by the committee member that authored the proposal of _Optional) in my /usr/local/include/:
https://github.com/chrisbazley/CBUtilLib/blob/main/Optional.h

It wraps libc APIs to add the qualifier where appropriate. And it indeed does this by necessity.

Cc: @chrisbazley

[alejandro-colomar]

@hallyn

How about changing the names of the structure members to be prefixed with io_ (or something else), similar to struct tm members being tm_*?