Request for short added documentation for "C++ Interface General"

[martin_n_fuller]

The documentation for "C++ Interface General" contains the following 
line:
"An important feature of the implementation is that an expression like 
a=b+c results in a single call to the corresponding mpz_add, without 
using a temporary for the b+c part. Expressions which by their nature 
imply intermediate values, like a=b*c+d*e, still use temporaries 
though."

I would like to extend it slightly, similar to below, after I bumped 
into the problem the hard way.
"An important feature of the implementation is that an expression like 
a=b+c results in a single call to the corresponding mpz_add, without 
using a temporary for the b+c part. Expressions which by their nature 
imply intermediate values, like a=b*c+d*e and (a+b>c), still use 
temporaries though, and these automatic temporaries may cause more 
memory allocations and slower performance than careful reuse of named 
variables."

Below is the good version of my program.  The bad version does not use 
tmp and instead uses the line "if ((a >> k) % k == 0) {". The bad 
version is significantly slower and causes millions of page faults from 
k=3800000 onwards (about 6 minutes).
I'm using GMP-6.3.0 on Cygwin with GCC 16.0.0.  Example compilation: g++ 
-o a073633 -std=c++26 -O3 -march=native -W -Wall a073633.cpp 
-L/usr/local/lib/ -lgmpxx -lgmp

#include <gmpxx.h>
int main() {
   mpz_class a = 1, tmp;
   unsigned n = 0;
   for (unsigned long k = 1; true; k++) {
     a *= 3;
     tmp = a >> k;
     tmp %= k;
     if (tmp == 0) {
       printf("a(%u)=%lu\n", ++n, k);
     }
     if (k % 100000 == 0) {
       fprintf(stderr, "%lu..", k);
     }
   }
}

Martin