g_flags_Group options generally don't affect the amount of debugging
information. -gsplit-dwarf is an exception. Its order dependency with
other gN_Group options make it inconvenient in a build system:
- -g0 -gsplit-dwarf -> level 2 -gsplit-dwarf "upgrades" the amount of debugging information despite the previous intention (-g0) to drop debugging information
- -g1 -gsplit-dwarf -> level 2 -gsplit-dwarf "upgrades" the amount of debugging information.
- If we have a higher-level -gN, -gN -gsplit-dwarf will supposedly decrease the amount of debugging information. This happens with GCC -g3.
The non-orthogonality has confused many users. This patch fixes the
problem by dropping the -g2 implication of -gsplit-dwarf. New semantics:
- If there is a g_Group, allow split DWARF. (There are still conditions split DWARF is disabled if it is not beneficial: -g0, -gline-directives-only, -g1 -fno-split-dwarf-inlining)
- Otherwise, no-op.
To restore the original behavior, replace -gsplit-dwarf with -gsplit-dwarf -g.