[Bug driver/80044] New: Specifying both -static and -pie insanity

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80044

            Bug ID: 80044
           Summary: Specifying both -static and -pie insanity
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: driver
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amodra at gmail dot com
  Target Milestone: ---

-static and -pie are incompatible, yet gcc neither warns nor errors on the
combination.  What's more, gcc's behaviour depends on whether gcc was built
with --enable-default-pie.

If gcc was built with --enable-default-pie then -static silently overrides an
explicit -pie, at least on x86 and I suspect most targets.  -static is passed
on to ld, gcc specifies the static startup files, and no -dynamic-linker is
passed to ld.  This is reasonable, but a warning that the explicit -pie was
overridden would be nicer.

If gcc was built with --disable-default-pie then -static does not fully
override -pie.  On x86, you get the static startup files, no -dynamic-linker,
and both -static and -pie are passed on to the linker.  ld.gold errors on that
combination.  ld.bfd tries to generate a PIE using the static startup files and
static (typically non-pic) libraries, and typically the wrong ld.so.  The wrong
ld.so leads to a somewhat cryptic "file not found" message on trying to run an
executable.  Non-pic startup and libraries result in a linker error on x86_64,
and text relocations on powerpc64le.  TEXTREL and ifunc as found in modern
glibc are fundamentally incompatible: When applying the text relocations, ld.so
makes the text segment temporarily writeable (and non-exec), but the text needs
to be exec to run ifunc resolvers.  A segfault before main is the result.