On 20 February 2014 10:02, Patrick Palka <patr...@parcs.ath.cx> wrote:
> On Thu, Feb 20, 2014 at 2:16 AM, Jonathan Wakely <jwakely....@gmail.com>
> wrote:
>> On 13 February 2014 20:47, Patrick Palka wrote:
>>> On a related note, would a patch to officially enable
>>> -Wmissing-declarations in the build process be well regarded?
>>
>> What would be the advantage?
>
> A missing declaration for an extern function definition likely means
> that the function should be marked static instead, so enabling the
> flag would help detect whether a function should otherwise be given
> static linkage. Isn't this especially important in libstdc++, where
> accidentally exposing an internal symbol in the library's ABI means
> having to keep the symbol around until the next ABI bump?
It's not really an issue for libstdc++. All symbols are internal by
default and we only export specifically chosen symbols. If a new
symbol accidentally matches an existing pattern in the linker script
then it will be noticed by the testsuite ('make check-abi' in the
$objdir/$target/libstdc++-v3 dir) and we will make the pattern more
specific.
Making some functions static might be worthwhile, but for the other
ones referred to in this quote from your first email:
> The rest of the
> fixes are on global function definitions whose declaration exists in a
> header file that was not included by the source file. To fix up these
> functions I simply included the relevant header file.
The only advantage of this change is that if the definition is changed
without also changing the header then you might get a failure during
compilation rather than linking, but even that isn't guaranteed as the
new definition could be interpreted as an overload rather than an
incompatible declaration.
Otherwise, including the header isn't *wrong* but it doesn't really
gain much, except silencing a warning, and that warning is only
emitted because you turned it on :-) And as you also said, some files
can't easily be fixed to avoid the warning. IMHO the simplest way to
solve the problem is not turn the warnings on!
Maybe others will disagree and will think enabling
-Wmissing-declarations would be a useful change, but I don't see the
point.
