Building

•   gcc-10 linker failure: "multiple definition of...".

  syslinux-6.04_pre1 fails to build on gcc-10 due to -fno-common change; gcc-10 (and above) flipped a default, from -fcommon to -fno-common.

  gcc-10 will reject multiple definitions of global variables. Possible/potential workaround: add/append -fcommon to CFLAGS. Ideally, the code would need a few 'extern' additions and maybe moving variable definitions.

•   undefined reference to `strlen'. Possibly related to (the link to) libc and/or to GCC-10+ optimizer. Solution: provide missing strlen() implementation in dos/string.h.
•   Prevent-pow-optimization when using gcc 8.2+.
•   internal error - lzo_init() failed! (inconsistent/sporadic error).

  Syslinux fails to build due to aliasing bugs in lzo. Add -fno-strict-aliasing to lzo/Makefile.

  References:

  • [1]

•   Fix broken efi binaries with binutils 2.31+.

  "Binutils >= 2.31 writes two PT_LOAD segments by default. This is not supported by the wrapper.c script used to convert the shared object into an elf binary."

  References:
  • "Patches from Debian" ( Lukas Schwaighofer )
  • Discard .note.gnu.property section to fix build failure (patch)
  • Patch: fix syslinux.efi (Re: Unable to get syslinux.efi to work, grub2 boots tho)
  • mk/efi: add -znoseparate-code to LD_FLAGS for EFI builds
•   If getting "Not enough room for program headers", try adding '--no-dynamic-linker' to the linker command line(s). Seen with binutils 2.27+. There might be other / better solutions / work-around methods.

  Note: 6.04-pre1+ should not be affected by this issue.

  Feedback is appreciated.

•  When building with glibc 2.23+, the "major", "minor" and "makedev" functions are defined in "sys/sysmacros.h". The patch "extlinux: pull in sys/sysmacros.h for major/minor/makedev", applied to Syslinux during 2016Apr, should help. Please note that not only Syslinux is affected by this change in glibc.

 Patches already included in Syslinux 6.04-pre1 (released 2016Mar):

• Building Syslinux 6.03 with gcc5+:
  • gcc fix alignment
  • don't guess sections' alignment
  • ldlinux: Fix return pointer to local data
• Use -mno-red-zone for EFI
• Syslinux 6.03 might fail to boot in some hardware (e.g. some Chromebooks). The patch "relocate protected-mode code as intended", applied to Syslinux during 2015Apr, might help.

Testing Syslinux 6.04-pre1 (or later) is recommended.

Other

• NASM 2.11.06 has a bug which prevents Syslinux from building correctly. Use other version of NASM (e.g. 2.11.05, 2.11.08+, among others).
• binutils 2.26, as originally released upstream, has a bug preventing Syslinux from building correctly. The bug in bintuils 2.26 was resolved in a later commit.

• "error: impossible constraint in asm". When gcc5+ is configured with --enable-default-pie, in some cases there might be a need to use custom flags in some makefile(s), similar to either "CFLAGS += -fno-pie" or "CFLAGS := -fno-pie". Examples:
  • [2]
  • [3] and [4]

See also

• Doc/building
• Development
• Contact