On 2021-01-08 13:36:26 +0000, Orians, Jeremiah (DTMB) wrote: > > If so, is libc malloc supposed to ensure alignment of allocated memory? > > According to https://man7.org/linux/man-pages/man3/malloc.3.html yes. > > @Janneke: So our mes libc malloc should be aligning the stuff--but it's not > > doing it. So it's a bug in our libc. > > Looks like you'll have to waste 3.7bytes on average per malloc to > always pad to the 8byte boundary.
Note that it's an 8-byte boundary for 32-bit systems, but a 16-byte boundary for 64-bit systems: https://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html And about the average waste, this depends on other factors (the main one may be that the block size is often a multiple of some power of two). -- Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
