ZipArchive::fromBuffer unconditionally deletes buffer

[PazerOP]

It appears this was bug was introduced in https://github.com/ctabin/libzippp/pull/38/files#diff-b5a89cdf6ac4efa657b832a52b38d47fR102. The libzip documentation for zip_source_buffer_create reads: "If freep is non-zero, the buffer will be freed when it is no longer needed."

As a result, this causes a crash/undefined behavior if it is not valid to delete the buffer when the ZipArchive is deleted.

[ctabin]

Hi @PazerOP and thanks for your report. Could you please post a small example where the described case occurs ?

[PazerOP]

Certainly.

#include <libzippp.h>

int main()
{
	const char* static_buffer = "my zip file, which is in a buffer that should not be deleted";

	auto archive = libzippp::ZipArchive::fromBuffer(static_buffer, strlen(static_buffer));

	delete archive; // Oh no! free(static_buffer) is called
}

This will crash during the delete because free is called on static_buffer. It doesn't matter that the "zip archive" in the buffer is invalid, this is just an example. Imagine that you have a pointer to a zip file in a memory mapped file, or you are managing the lifetime of the buffer yourself.