https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84193
Bug ID: 84193
Summary: Document the limitations of -fcheck-pointer-bounds
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: bruno at clisp dot org
Target Milestone: ---
The documentation of -fcheck-pointer-bounds in
https://gcc.gnu.org/onlinedocs/gcc-7.3.0/gcc/Instrumentation-Options.html says
- what the option does,
- what are the prerequisites from other tools,
- how it can be fine-tuned.
However, it does not say what are the limitations.
=== Quoting the article "Design of Intel MPX" from Intel
<https://intel-mpx.github.io/design/>:
"At the application level, the MPX-protected program may require manual changes
due to troublesome C coding patterns, multithreading issues, or potential
problems with other ISA extensions. (In some cases, it is inadvisable to use
MPX at all.)"
"the protected application will have worse cache locality"
"Intel MPX can cause issues when used together with other ISA extensions, e.g.,
Intel TSX and Intel SGX. Intel MPX may cause transactional aborts in some
corner cases when used inside an Intel TSX hardware transaction ..."
"our evaluation reveals that narrowing of bounds breaks many programs (see
Usability)..." (The entire section "Not supported C idioms" is relevant.)
=== Quoting Florian Weimer, a glibc co-maintainer
<https://lists.gnu.org/archive/html/bug-gnulib/2018-02/msg00015.html>:
"-fcheck-pointer-bounds in GCC doesn't really work. The existing implementation
is barely a research prototype (for example, most string functions are not
protected by it), and I don't think anyone knows how to make it thread-safe."
Really, as a user of GCC, I would like to be made aware of these limitations
through the GCC documentation, so that I don't waste my time attempting to use
a technology that will not work with my application.
