https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108622
Bug ID: 108622
Summary: x86 -fno-pic: use DW_EH_PE_indirect|DW_EH_PE_pcrel for
personality/ttype encoding
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: i at maskray dot me
Target Milestone: ---
In .eh_frame and .gcc_except_table, the aarch64 and riscv ports use
DW_EH_PE_indirect|DW_EH_PE_pcrel for both -fno-pic and PIC code to avoid
canonical PLT entry/copy relocation, if the personality and typeinfo objects
are defined in a shared object (common case, libstdc++.so.6 or libc++.so.?).
AIUI there is no drawback other than a negligible size increase.
% g++ -fno-pic -no-pie -fuse-ld=bfd a.cc -o a
% readelf -Wr a | grep COPY
0000000000403db8 0000000900000005 R_X86_64_COPY 0000000000403db8
_ZTIi@CXXABI_1.3 + 0
0000000000403dc8 0000000800000005 R_X86_64_COPY 0000000000403dc8
_ZTIPKc@CXXABI_1.3 + 0
% readelf -W --dyn-syms a | grep __gxx_personality_v
10: 0000000000401060 0 FUNC GLOBAL DEFAULT UND
__gxx_personality_v0@CXXABI_1.3 (2)
% g++ -fpic -no-pie -fuse-ld=bfd a.cc -o a
% readelf -Wr a | grep COPY
% readelf -W --dyn-syms a | grep __gxx_personality_v0
7: 0000000000000000 0 FUNC GLOBAL DEFAULT UND
__gxx_personality_v0@CXXABI_1.3 (2)
Essentially this applies -mno-direct-extern-access unconditionally to -fno-pic,
cleaning up gcc/config/i386/i386.cc:asm_preferred_eh_data_format
