https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80826
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I don't know why it's so slow, or if it's possible to change the libstdc++ code
to help the c++98 case (I doubt it).
But it helps a lot if you insert the correct type:
mMap.insert (std::pair<const std::string, int>("1", 1));
The value_type of map<K, T> is pair<const K, T> not pair<K, T>. Inserting the
wrong type means the compiler instantiates two different specializations of
std::pair and has to convert from one to the other.
With -O1 the time-report for that is:
TOTAL : 348.27 2.37 351.29 1595960 kB
That's still slow, but not "making the box unusable" slow.
It helps a bit more if you create an array of pairs and insert from that:
std::pair<const std::string, int> pairs[] = {
std::pair<const std::string, int>("1", 1),
...
};
int n = sizeof(pairs)/sizeof(pairs[0]);
std::map<std::string, int> mMap(pairs, pairs + n);
With -O1 the time-report for that is:
TOTAL : 178.28 1.66 180.50 1071340 kB
Both runs print:
m.cc:6:5: note: variable tracking size limit exceeded with
-fvar-tracking-assignments, retrying without
