https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44107
--- Comment #36 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-9 branch has been updated by Iain D Sandoe <ia...@gcc.gnu.org>: https://gcc.gnu.org/g:6cfcaa4609ee3e3557ddf50fda00fdf9a5fc07e4 commit r9-9492-g6cfcaa4609ee3e3557ddf50fda00fdf9a5fc07e4 Author: Iain Sandoe <i...@sandoe.co.uk> Date: Mon Jan 18 20:09:10 2021 +0000 dwarf2unwind : Force the CFA after remember/restore pairs [44107/48097]. This address one of the more long-standing and serious regressions for Darwin. GCC emits unwind code by default on the assumption that the unwinder will be (of have the same capability) as the one in the current libgcc_s. For Darwin platforms, this is not the case - some of them are based on the libgcc_s from GCC-4.2.1 and some are using the unwinder provided by libunwind (part of the LLVM project). The latter implementation has gradually adopted a section that deals with GNU unwind. The most serious problem for some of the platform versions is in handling DW_CFA_remember/restore_state pairs. The DWARF description talks about these in terms of saving/restoring register rows; this is what GCC originally did (and is what the unwinders do for the Darwin versions based on libgcc_s). However, in r118068, this was changed so that not only the registers but also the current frame address expression were saved. The unwind code assumes that the unwinder will do this; some of Darwin's unwinders do not, leading to lockups etc. To date, the only solution has been to replace the system libgcc_s with a newer one which is not a viable solution for many end-users (since that means overwritting the one provided with the system installation). The fix here provides a target hook that allows the target to specify that the CFA should be reinstated after a DW_CFA_restore. This fixes the issue (and also the closed WONTFIX of 44107). (As a matter of record, it also fixes reported Java issues if backported to GCC-5). gcc/ChangeLog: PR target/44107 PR target/48097 * config/darwin-protos.h (darwin_should_restore_cfa_state): New. * config/darwin.c (darwin_should_restore_cfa_state): New. * config/darwin.h (TARGET_ASM_SHOULD_RESTORE_CFA_STATE): New. * doc/tm.texi: Regenerated. * doc/tm.texi.in: Document TARGET_ASM_SHOULD_RESTORE_CFA_STATE. * dwarf2cfi.c (connect_traces): If the target requests, restore the CFA expression after a DW_CFA_restore. * target.def (TARGET_ASM_SHOULD_RESTORE_CFA_STATE): New hook. (cherry picked from commit 491d5b3cf8216f9285a67aa213b9a66b0035137b)
