On Sat, Jan 17, 2026 at 11:44:20PM +0100, Alejandro Colomar wrote:

On Sat, Jan 17, 2026 at 11:37:08PM +0100, Alejandro Colomar wrote:

quoted

Hi Mark,

On Sat, Jan 17, 2026 at 02:23:39PM -0800, Mark Harris wrote:

quoted

"e" seems like a particularly poor choice, given that it is used in
documentation with the well-established meaning of the base of the
natural logarithm (e.g., in exp(3)).

I don't expect anyone to confuse a variable 'e' with the base of the
natural logarithm (M_E from <math.h>), since the base of the natural
logarithm is not something variable, and thus it wouldn't make sense to
pass it as a function argument.

Maybe a second of wondering, and reading the documentation carefully,
but nothing important.  Once the base of the natural logarithm is
discarded the meaning is then clear.  On the other hand, I would
consistently wonder what 'p' is, as it has no mnemonics.

One may argue that 'ex' might be even better than any of exp/e/p.

Actually, I see now that 'p' could stand for power.  Not too bad, then.

quoted

quoted

 - Mark

Have a lovely night!
Alex

quoted

Alejandro Colomar wrote:

quoted

Hi!


I see n3704 attempts to fix the issues reported by Vincent; that's good.
<https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3704.pdf>

However, the paper renames the pointer to 'p', which doesn't seem to
have good mnemonics nor relate to what it is.  'p' seems to just be
for 'pointer'?  We can and should do better.

I think alx-0051 was better, in using a parameter name that relates to
what the parameter means: 'e' for exponent.  Names matter.

I think we should discuss the name in the meeting.  Also, I think n3704
should have included a rationaly for the name; especially, when a better
name has been proposed, and for some reason the proposal decided to use
a different one; that should certainly have been discussed.

I think we can discuss the name in meeting without having to officially
present alx-0051 with an N-document number.  Please let me know if I
should formally present alx-0051 for the next meeting.


Have a lovely night!
Alex

On Tue, Jul 15, 2025 at 12:24:29AM +0200, Alejandro Colomar wrote:

quoted

Hi!

Vincent reported this issue to me in the Linux man-pages mailing list
(as the manual pages also had the same issue, so he reported the issue
in both the manual pages and the ISO C standard).  I think this can be
fixed editorially without going through an official N-document.  Please
find the proposal below.


Have a lovely night!
Alex

---
Name
      alx-0051r0 - don't misuse reserved identifier 'exp'

Category
      Editorial.

Author
      Reported-by: Vincent Lefevre [off-list ref]
      Signed-off-by: Alejandro Colomar [off-list ref]

History
      <https://www.alejandro-colomar.es/src/alx/alx/wg14/alx-0051.git/>

      r0 (2025-07-15):
      -  Initial draft.

Rationale
      Since 'exp' is a library function, it is a reserved identifier,
      which should not be used as a variable / parameter name.

      7.1.3p1 says

              All potentially reserved identifiers (...) that are
              provided by an implementation with an external
              definition are reserved for any use.

Proposed wording
      Based on N3550.

    7.17.7.5  The atomic_compare_exchange generic functions
      @@ Description, p7 EXAMPLE
      -       exp = atomic_load(&cur);
      +       e = atomic_load(&cur);
              do {
      -               des = function(exp);
      +               des = function(e);
      -       } while (!atomic_compare_exchange_weak(&cur, &exp, des));
      +       } while (!atomic_compare_exchange_weak(&cur, &e, des));

    B.11  Mathematics <math.h>
      @@
      ...
      -_FloatN frexpfN(_FloatN value, int *exp);
      -_FloatNx frexpfNx(_FloatNx value, int *exp);
      -_DecimalN frexpdN(_DecimalN value, int *exp);
      -_DecimalNx frexpdNx(_DecimalNx value, int *exp);
      +_FloatN frexpfN(_FloatN value, int *e);
      +_FloatNx frexpfNx(_FloatNx value, int *e);
      +_DecimalN frexpdN(_DecimalN value, int *e);
      +_DecimalNx frexpdNx(_DecimalNx value, int *e);
      ...

      @@
      ...
      -_FloatN ldexpfN(_FloatN value, int *exp);
      -_FloatNx ldexpfNx(_FloatNx value, int *exp);
      -_DecimalN ldexpdN(_DecimalN value, int *exp);
      -_DecimalNx ldexpdNx(_DecimalNx value, int *exp);
      +_FloatN ldexpfN(_FloatN value, int *e);
      +_FloatNx ldexpfNx(_FloatNx value, int *e);
      +_DecimalN ldexpdN(_DecimalN value, int *e);
      +_DecimalNx ldexpdNx(_DecimalNx value, int *e);
      ...

      @@
      ...
      -_FloatN scalbnfN(_FloatN value, int *exp);
      -_FloatNx scalbnfNx(_FloatNx value, int *exp);
      -_DecimalN scalbndN(_DecimalN value, int *exp);
      -_DecimalNx scalbndNx(_DecimalNx value, int *exp);
      +_FloatN scalbnfN(_FloatN value, int *e);
      +_FloatNx scalbnfNx(_FloatNx value, int *e);
      +_DecimalN scalbndN(_DecimalN value, int *e);
      +_DecimalNx scalbndNx(_DecimalNx value, int *e);
      -_FloatN scalblnfN(_FloatN value, int *exp);
      -_FloatNx scalblnfNx(_FloatNx value, int *exp);
      -_DecimalN scalblndN(_DecimalN value, int *exp);
      -_DecimalNx scalblndNx(_DecimalNx value, int *exp);
      +_FloatN scalblnfN(_FloatN value, int *e);
      +_FloatNx scalblnfNx(_FloatNx value, int *e);
      +_DecimalN scalblndN(_DecimalN value, int *e);
      +_DecimalNx scalblndNx(_DecimalNx value, int *e);
      ...

    F.10.4.9  The ldexp functions
      @@ p1
       On a binary system,
      -ldexp(x, exp)
      +ldexp(x, e)
       is equivalent to
      -scalbn(x, exp).
      +scalbn(x, e).

      ## And remove bold from 'exp' in the paragraph above.  This is
      ## probably present due to exp being considered as a reserved
      ## identifier by some script, which is part of the consequences
      ## of undefined behavior: UB might format your standard!  :)

    H.11.3  Functions
      @@ 7.12.7  Exponential and logarithmic functions
      ## Apply same changes as in B.11 (see above).

      @@ F.10.14  Payload functions, p2
      ...
       the exponent is an integral power of 2 and,
       when applicable,
      -value equals x × 2*exp.
      +value equals x × 2*e.

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