compile options

[jmbnyc]

Is it a requirement to compile pcre2 source code with -mshstk (shadow stack)?

[zherczeg]

No. Is there a project where it is a requirement?

[jmbnyc]

No requirement at all inside my code.
I asked because after generating pcre2 Makefile (from version 10.44) I noticed the following:

echo " CC " src/libpcre2_8_la-pcre2_compile.lo;/bin/bash ./libtool --silent --tag=CC --mode=compile gcc -DHAVE_CONFIG_H -I. -I./src "-I./src" -DPCRE2_CODE_UNIT_WIDTH=8 -fvisibility=hidden -mshstk -O2 -MT src/libpcre2_8_la-pcre2_compile.lo -MD -MP -MF src/.deps/libpcre2_8_la-pcre2_compile.Tpo -c -o src/libpcre2_8_la-pcre2_compile.lo test -f 'src/pcre2_compile.c' || echo './'src/pcre2_compile.c

The presence of -mshstk caught my eye and was wondering if it is a required flag. I am thinking of pulling the pcre2 source directly into my binary (no library) and thus need to provide the appropriate compile flags and we currently do not have -mshstk as a compile option and I'd like to keep it that way.

[PhilipHazel]

That's odd. A simple ./configure on 10.44 gives just this:

C compiler flags ................... : -O2 -fvisibility=hidden

[NWilson]

There's this in the changelog:

Version 10.36 04-December-2020

1. Add CET_CFLAGS so that when Intel CET is enabled, pass -mshstk to
   compiler. This fixes https://bugs.exim.org/show_bug.cgi?id=2578. Patch for
   Makefile.am and configure.ac by H.J. Lu. Equivalent patch for CMakeLists.txt
   invented by PH.

I guess the user is using Intel CET?

[zherczeg]

Shadow stack can be used as a security feature, and even jit supports it. Although I never tested it, the code was a contribution from Intel.

However, it is not a mandatory feature for PCRE2, and there is no reason to be that way, ever.