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https://issues.apache.org/jira/browse/STDCXX-492?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Travis Vitek updated STDCXX-492:
--------------------------------
Attachment: string.patch
Patch improves times of both basic_string<>::append() and
basic_string<>::op+=().
I've looked at the gnu changelog format description, and it doesn't mention
what to do when you are changing multiple overloads of the same functions. I'm
guessing, here, but if that is wrong, please correct me.
2007-09-24 Travis Vitek <[EMAIL PROTECTED]>
STDCXX-492
* string (operator+=): replace call to append with push_back
for performance.
(append): avoid calling replace() from append if there is
sufficient buffer space available for performance.
(append): simplify append overload, move it to header and then
inline it.
(append): use _RWSTD_SIZE_T to avoid integer overflow problems
that could lead to heap corruption.
(push_back): call replace() instead of append when buffer
reallocation required. cleanup. avoid integer overflow problem.
* string.cc (append): moved append overload to header and make
it inline.
> std::string::operator+=() slow
> ------------------------------
>
> Key: STDCXX-492
> URL: https://issues.apache.org/jira/browse/STDCXX-492
> Project: C++ Standard Library
> Issue Type: Bug
> Components: 21. Strings
> Affects Versions: 4.1.3
> Environment: gcc 4.1.2 on Linux/x86_64
> Reporter: Mark Brown
> Assignee: Travis Vitek
> Fix For: 4.2
>
> Attachments: string.patch
>
>
> Comparing overloads of string::operator+=() in stdcxx with the same functions
> in gcc 4.1.2, stdcxx is up to twice slower than gcc:
> $ time ./op_plus_equal-stdcxx 100000000 0
> real 0m2.241s
> user 0m1.932s
> sys 0m0.204s
> $ time ./op_plus_equal-stdcxx 100000000 1
> real 0m2.540s
> user 0m2.344s
> sys 0m0.196s
> $ time ./op_plus_equal-stdcxx 100000000 2
> real 0m1.492s
> user 0m1.308s
> sys 0m0.184s
> $ time ./op_plus_equal-gcc 100000000 0
> real 0m0.883s
> user 0m0.728s
> sys 0m0.156s
> $ time ./op_plus_equal-gcc 100000000 1
> real 0m1.589s
> user 0m1.424s
> sys 0m0.168s
> $ time ./op_plus_equal-gcc 100000000 2
> real 0m1.131s
> user 0m0.976s
> sys 0m0.156s
> #include <cassert>
> #include <cstdlib>
> #include <string>
> int main (int argc, char *argv[])
> {
> const int N = argc < 2 ? 1 : std::atoi (argv [1]);
> const int op = argc < 3 ? 0 : std::atoi (argv [2]);
> std::string str;
> const std::string x ("x");
> if (op == 0) {
> for (int i = 0; i < N; ++i)
> str += 'x';
> } else if (op == 1) {
> for (int i = 0; i < N; ++i)
> str += "x";
> } else {
> for (int i = 0; i < N; ++i)
> str += x;
> }
> assert (str.size () == std::size_t (N));
> }
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