Dominique Pellé wrote:

Hi

I see code like this in an application to iterate over files in a directory with boost::filesystem (v1.70) without using exceptions:

boost::filesystem::path dir("somedir"); boost::system::error_code error; boost::filesystem::directory_iterator node(dir, error), end;

if (error) { return ...; } for (; node != end; node.increment(error)) { const boost::filesystem::path& path = node->path(); // ... }

It appears to work... or mostly work since a crash was reported and the stack points to this area of the code. It's a rare crash that I could not reproduce myself.

I suspect that there is a bug in the above code and it should instead be:

boost::filesystem::path dir("somedir"); boost::system::error_code error; boost::filesystem::directory_iterator node(dir, error), end;

for (; !error && node != end; node.increment(error)) { const boost::filesystem::path& path = node->path(); // ... }

In other words, I suspect that we need to check that node.increment(error) in the for loop did not give an error before checking the condition "node != end", or else we may enter the loop in case of error and then it may access node->path() with an invalid node iterator.

I could not find in the doc at ... https://www.boost.org/doc/libs/1_75_0/libs/filesystem/doc/reference.html ... what exactly happens when node.increment(error) gives an error. Perhaps the doc deserves clarification or an example illustrating how to reliably iterate over files without using exceptions would be welcome.

Replying to self: stumbling upon ticket https://github.com/boostorg/filesystem/issues/112 the last comment there indicates that it's undefined whether the iterator should progress or not in case of error. So I think my fix is correct. I.e. for (; node != end; node.increment(error)) { ...} ... should be: for (; !error && node != end; node.increment(error)) { ...} The documentation deserves clarification in my opinion. Regards Dominique