Use `-fasynchronous-unwind-tables' rather than `-fexceptions
-fnon-call-exceptions' in LIB2_DIVMOD_FUNCS compilation flags so as to
provide unwind tables for the affected functions while not pulling the
unwinder proper, which is not required here.
Beyond saving program space it fixes a RISC-V glibc build error due to
unsatisfied `malloc' and `free' references from the unwinder causing
link errors with `ld.so' where libgcc has been built at -O0.
libgcc/
* config/riscv/t-elf (LIB2_DIVMOD_EXCEPTION_FLAGS): New
variable.
---
Hi,
As Mon, Aug 31st (a bank holiday in England) will be my last day at
Western Digital and I won't be able to submit patches on behalf of the
company afterwards here is a replacement change for RISC-V only in case
the generic one discussed here:
<https://gcc.gnu.org/pipermail/gcc-patches/2020-August/552327.html
does not go through. While I won't be able to submit changes I will
continue watching the discussion and I will be able to commit either
change once there is the final outcome, just as anyone would.
This change has passed full GCC regression testing with the
`riscv64-linux-gnu' target, RV64/lp64d and RV32/ilp32d multilibs, using
QEMU in the Linux user emulation mode.
Maciej
---
libgcc/config/riscv/t-elf | 2 ++
1 file changed, 2 insertions(+)
gcc-riscv-libgcc-divmod-asynchronous-unwind-tables.diff
Index: gcc/libgcc/config/riscv/t-elf
===================================================================
--- gcc.orig/libgcc/config/riscv/t-elf
+++ gcc/libgcc/config/riscv/t-elf
@@ -4,3 +4,5 @@ LIB2ADD += $(srcdir)/config/riscv/save-r
$(srcdir)/config/riscv/div.S \
$(srcdir)/config/riscv/atomic.c \
+# Avoid the full unwinder being pulled along with the division libcalls.
+LIB2_DIVMOD_EXCEPTION_FLAGS := -fasynchronous-unwind-tables
