On 7 October 2010 22:43, Aaron Graham <aaron@aarongraham.com> wrote:
I'm excited about construe_cast. I always liked the flexibility of lexical_cast, but tend not to use it as much as I could because of its performance relative to other mechanisms. Does gcc still convert "23" at compile time if you disable builtins? (-fno-builtin)
#include <boost/construe_cast.hpp> int main(int, char**) { return boost::construe_cast<int>("23"); } compiled using gcc 4.5.1, g++-4.5 test.cpp -o test -O3 -I . -I ../library/boost-trunk/ -fno-builtin will generate the following code: Dump of assembler code for function main: 0x0000000100000e20 <main+0>: push %rbp 0x0000000100000e21 <main+1>: mov $0x17,%eax 0x0000000100000e26 <main+6>: mov %rsp,%rbp 0x0000000100000e29 <main+9>: leaveq 0x0000000100000e2a <main+10>: retq 0x0000000100000e2b <main+11>: nopl 0x0(%rax,%rax,1) thus as you can see, it's still able to perform the optimization. Jeroen