Correct last compilation warnings in readpassphrase

[benrubson]

Hi,

This PR corrects last compilation warnings regarding readpassphrase.cpp.
It comes back to the original file, simply adding a dummy test to avoid the (void)write() warnings.
Will then help to progress on #426.

/home/makerpm/rpmbuild/BUILD/encfs-master/encfs/readpassphrase.cpp:128:46: warning: ignoring return value of 'ssize_t write(int, const void*, size_t)', declared with attribute warn_unused_result [-Wunused-result]
   (void)write(output, prompt, strlen(prompt));
                                              ^
/home/makerpm/rpmbuild/BUILD/encfs-master/encfs/readpassphrase.cpp:149:33: warning: ignoring return value of 'ssize_t write(int, const void*, size_t)', declared with attribute warn_unused_result [-Wunused-result]
     (void)write(output, "\n", 1);
                                 ^

Thank you !

[vgough]

I'd rather not maintain a custom version of readpassphrase. Do you know if upstream versions of this code still produce warnings?

[benrubson]

Yes, I had a look, it does.
Finally I just transformed :
(void)write
into :
if(write) {}
To avoid compilation warnings of non-checked returned value.

[rfjakob]

Shouldn't we error out if the write fails?

[benrubson]

It's the write() which outputs the password prompt, so I think this is why it is simply not checked, password can be get even if prompt is not shown 👍

[benrubson]

If we look at the modifications finally made to this upstream file, they are rather tiny :

The 2 write calls :

(void)write(output, prompt, strlen(prompt));

Have simply been changed to :

if (write(output, prompt, strlen(prompt)) != -1) {
  //dummy test to get rid of warn_unused_result compilation warning
}

That's it 👍
And this allows us to get rid of warning messages.
It's worth it I think :)

[vgough]

Looks to me like a few things have changed. I've created a PR #425 to import a new version. I don't see any compiler warnings when building.

[benrubson]

At least if we could commit this @vgough to get rid of compilation warnings + clang warnings visible in master CI, I think it would be perfect 👍
Then we could think about the update ?
Many thanks 👍

[vgough]

ok, go for it.

[benrubson]

Many thanks @vgough 👍