Avoid manually coding the rule to build crasher, instead fuddle
the compiler so that even -O2 optimization does not eliminate call
to b().
First, put calls to both a() and b() in the b() into non-tail-recursive
position. Second, as recommended in gcc manual, use asm volatile("");
to prevent further prevent inlining, besides attribute((noinline).
And third, call b() by alias, which current gcc optimizer cannot see
through.
Also, do not dereference NULL in a, and mark the memory access as volatile.
[ Minor portability improvements: asharma@fb.com ]
Program test-coredump-unwind was modified to map backing files based on
virtual addresses instead of segment numbers.
The crasher.c is a program that essentially calls some functions and
then writes to invalid address causing a crash. Before that, it detects
which executables are mapped to which virtual addresses and writes this
information to a file suitable for consumption by test-coredump-unwind.
The mapping information is obtained form /proc/self/maps, so currently
it only works on linux.
The test itself is a shell script, which first runs the program and then
runs test-coredump-unwind on the resulting core and address space
map file to check whether the stack trace obtained from the dump roughly
corresponds to what it should look like.
Signed-off-by: Martin Milata <mmilata@redhat.com>
