[llvm-dev] LTO prevention help

[Jon Slenk via llvm-dev]

I'm trying to learn about LTO. I have a static variable that I try to give
a non-compile-time-constant value to. With LTO turned off, the sprintf
happens i.e. a breakpoint set on that line does get triggered. With LTO
turned on (either Monolithic or Incremental), the code appears to be
removed/elided/deleted/forgotten/dropped/lost/ignored and the breakpoint is
never tripped.

What can I do to make my code survive through LTO? The variable makes it
through but the sprinf() line doesn't. Can I somehow tell LTO to not apply
to this function or line of code or file of code? (In reality this is
something I am trying to do via Xcode for iOS targets.)

thank you.


   1. static void __attribute__((constructor))_initv1 () {
   2.     static char default_[] =
   "0000000000000000000000000000000000000000000000000000000000000000";
   3.     sprintf( default_, "%lu", (unsigned long)5 );
   4. }
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