The memory layout of a real*10 variable on an i386 processor requires 12 or 16
bytes per variable, depending on the flag -m128bit-long-double. The disk
layout for unformatted (binary) writing occupies 10 bytes per variable.
This has several disadvantages. It is different from I would naively expect
(which does not mean much), and it is different from binary C I/O (which could
also be ignored). However, it is likely also rather inefficient if large
arrays are written to disk, because a single call to write() or fwrite() now
has to be split up into one call per array element, so that the padding is
removed.
It is also questionable whether having a real*10 variable occupy 12 or 16
bytes in memory is what people expect; again, this could be ignored since the
standard permits this. However, this is also very different from what other
compilers do.
--
Summary: Memory and binary disk layout disagree for real*10
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: schnetter at aei dot mpg dot de
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22519
