sprintf '#' flag with %o does not conform to POSIX

[dmaestro]

Assuming we don't want to depart from POSIX behavior in our sprintf function.

The # flag with %o and precision is described in Perl 6 Documentation to follow POSIX by conditionally padding beyond the given precision, only if necessary to preserve the c-style 0-prefix on the octal output.
My linux stdio lib follows this behavior:

doug@ender:~/study/Perl6$ echo -e '#include <stdio.h>\n#include <iostream>\nusing namespace std;\n
int main() { char* s = new char[10]; sprintf(s, "%#.5o\\n", 012345); cout<<s; }' | gcc -x c++ -lstdc++ - ; ./a.out
012345
doug@ender:~/study/Perl6$ echo -e '#include <stdio.h>\n#include <iostream>\nusing namespace std;\n
int main() { char* s = new char[10]; sprintf(s, "%.5o\\n", 012345); cout<<s; }' | gcc -x c++ -lstdc++ - ; ./a.out
12345
doug@ender:~/study/Perl6$ echo -e '#include <stdio.h>\n#include <iostream>\nusing namespace std;\n
int main() { char* s = new char[10]; sprintf(s, "%#.5o\\n", 0123); cout<<s; }' | gcc -x c++ -lstdc++ - ; ./a.out
00123
doug@ender:~/study/Perl6$ echo -e '#include <stdio.h>\n#include <iostream>\nusing namespace std;\n
int main() { char* s = new char[10]; sprintf(s, "%.5o\\n", 0123); cout<<s; }' | gcc -x c++ -lstdc++ - ; ./a.out
00123

However, Rakudo Perl6 departs from this behavior:

[13:11] <dmaestro> m: say sprintf "%.5o", 0o123
[13:11] <camelia> rakudo-moar c95c4a: OUTPUT: «00123␤»
[13:11] <dmaestro> m: say sprintf "%#.5o", 0o123
[13:11] <camelia> rakudo-moar c95c4a: OUTPUT: «000123␤»   # uh-uh
[13:11] <dmaestro> m: say sprintf "%.5o", 0o12345
[13:11] <camelia> rakudo-moar c95c4a: OUTPUT: «12345␤»
[13:12] <dmaestro> m: say sprintf "%#.5o", 0o12345
[13:12] <camelia> rakudo-moar c95c4a: OUTPUT: «012345␤»