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Re: TR library extensions
Gabriel Dos Reis wrote:
Pétur Runólfsson <peturr02@ru.is> writes:
| Gabriel Dos Reis wrote:
| > | A -std= option is needed that adds include/tr1 to the include path,
| > | because the new tr1 headers should not be visible if -std=c++98 is
| > | given.
| >
| > Why?
|
| Consider the program
|
| #include <tuple>
| int main() { }
|
| The documentation for the -std switch says:
| Specify the standard to which the code should conform
| This code doesn't conform to C++ 98 (because there is no header named
| <tuple>). Shouldn't the compiler reject it when -std=c++98 is
| specified?
I see no reason. Do you also propose to reject
#include <unistd.h>
FWIW, the reason to reject the program above is for strict conformance
(i.e., to make it easier to detect programs that are not portable to
other implementations). The difference between your example and the
one given by Petur is that the <unistd.h> header doesn't come with gcc
while <tuple> presumably will. Gcc has little control over the headers
that come with the operating system (and the conformance of those to
the various standards is left up to their implementors, and in POSIX
is typically controlled by macros such as _POSIX_VERSION, etc.), but
it does have complete control over its own implementation of the
language.
So I agree with Petur: a quality implementation of C++ such as gcc
should provide an option for programs to choose the version of the
C++ standard they want to conform to, and the compiler should
diagnose detectable violations when the option is selected.
Regards
Martin