Thanks Floh, I was hoping to find the equivalent of Windows's _aligned_msize which returns the exact allocated memory but I guess I can live with malloc_usable_size for now.
On Thursday, August 6, 2015 at 5:59:46 AM UTC+8, Floh wrote: > > AFAIK there is no standard way to query the size you passed in to malloc() > by the returned pointer, even malloc_usable_size is not standard. > > malloc_usable_size() may return a larger size, but I definitely wouldn't > count on that this is always 4 (see here: > http://man7.org/linux/man-pages/man3/malloc_usable_size.3.html). > > Some platforms or allocator libs have an msize() or _msize() function, but > I haven't found this in the dlmalloc sources. > > If you absolutely need to store the size passed to alloc inside a memory > block then I think you need to implement this on your own (allocate > additional space for a header, store size in header, and return pointer > after header). This will be dangerous though if you cannot guarantee that > all alloc/free calls are properly paired and go through your own wrapper > functions. > > Cheers, > -Floh. > > Am Mittwoch, 5. August 2015 12:29:03 UTC+2 schrieb awt: >> >> Hi, >> >> I need to retrieve the size of a buffer that is dynamically allocated and >> this is what I did: >> >> >> size_t size = 64; >> size_t alignment = 8; >> memalign(alignment, size); >> >> size_t measuredSize = malloc_usable_size(test); >> std::cout << "measuredSize:" << measuredSize << " size:" << size << >> std::endl; >> >> However, the size returned by malloc_usable_size is always 4 more than >> the amount that I pass in to memalign. In this case, measuredSize will be >> 68. I tried using malloc and the result is the same. >> >> Is there a way to get the size that I pass into memalign or can I always >> assume that malloc_usable_size will always report a higher size of 4 bytes? >> > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
