[Bug 1940029] Re: Default of fcf-protection should only be enabled where it can work

[Launchpad Bug Tracker]

This bug was fixed in the package gcc-11 - 11.2.0-19ubuntu1

---------------
gcc-11 (11.2.0-19ubuntu1) jammy; urgency=medium

  * Merge with Debian; remaining changes:
    - Build from upstream sources.

gcc-11 (11.2.0-19) unstable; urgency=medium

  * Update to git 20220324 from the gcc-11 branch.
    - Fix PR tree-optimization/101636, PR tree-optimization/104782,
      PR tree-optimization/104931, PR target/105000 (x86),
      PR target/104890 (x86), PR target/104998 (x86), PR target/104923 (PPC),
      PR target/87496 (PPC), PR target/104208 (PPC), PR target/104963 (x86),
      PR middle-end/100775, PR middle-end/104786, PR tree-optimization/104511,
      PR target/104453 (x86), PR middle-end/104402, PR debug/104337,
      PR tree-optimization/103641, PR target/99708 (PPC),
      PR rtl-optimization/104777, PR target/104219 (RISCV),
      PR target/99708 (PPC), PR target/104253 (PPC),
      PR tree-optimization/102819, PR tree-optimization/103169, PR ada/104861,
      PR c++/103186, PR c++/103057, PR c++/59950, PR c++/101095, PR c++/58646,
      PR c++/103337, PR c++/102740, PR c++/103299, PR c++/102538,
      PR c++/101767, PR c++/104667, PR d/105004, PR fortran/99585,
      PR fortran/104430, PR fortran/96983, PR fortran/104811, PR d/104659.
  * Don't enable -fcf-protection with -m16. LP: #1940029.

 -- Matthias Klose <doko at ubuntu.com>  Thu, 24 Mar 2022 15:22:07 +0100

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https://bugs.launchpad.net/bugs/1940029

Title:
  Default of fcf-protection should only be enabled where it can work

Status in gcc-10 package in Ubuntu:
  Fix Released
Status in gcc-11 package in Ubuntu:
  Fix Released
Status in gcc-12 package in Ubuntu:
  Fix Committed
Status in qemu package in Ubuntu:
  Fix Released

Bug description:
  Hi,
  I've happened to find this breaking a qemu build that was breaking like:

  
  c -MMD -MP -MT linuxboot_dma.o -MF ./linuxboot_dma.d -O2 -g -march=i486 -Wall -Wstrict-prototypes -Wredundant-decls -Wundef -Wwrite-strings -Wmissing-prototypes -Wformat -Werror=format-security -Wdate-time -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -fno-pie -ffreestanding -I/<<PKGBUILDDIR>>/pc-bios/optionrom//../../include   -fno-stack-protector   -m16   -Wa,-32 -c /<<PKGBUILDDIR>>/pc-bios/optionrom/linuxboot_dma.c -o linuxboot_dma.o
  cc1: error: ‘-fcf-protection’ is not compatible with this target                 

  As usual this looks complex but it can be reduced to your favorite C
  hello world.

  It should work if you build it with:
    $ cc -Wall -Werror test.c -o test.o

  But the following will fail:
    $ cc -Wall -Werror -march=i486 -m16 test.c -o test.o
  cc1: error: ‘-fcf-protection’ is not compatible with this target

  
  This is some of the always crazy boot blobs that virtualization needs here and there - and I hope I can resolve it for qemu in the build. But in general while I think the fcf default (https://wiki.ubuntu.com/ToolChain/CompilerFlags#A-fcf-protection) is ok, it should not be default on arch combinations where it can never work.

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