On 05/10/18 13:27, Kyrill Tkachov wrote: > Hi Alex, > > I'm forwarding this to the gcc-help list which is the appropriate place > for this discussion. > gcc-bugs is for automated emails from the bug tracker and your mail is > likely to get lost in there. > > Thanks, > Kyrill > > On 05/10/18 13:24, Alexander Fedotov wrote: >> Hello >> >> I've noticed that for C++ translation unit GCC for aarch64 always >> emits CFI into eh_frame but never debug_frame even if debug >> information is enabled. Tried on GCC versions 6 to 8. >> DWARF for the ARM 64-bit architecture (AArch64) states that it must be >> debug_frame >> ((https://static.docs.arm.com/ihi0057/b/IHI0057B_aadwarf64.pdf) >> GAS supports emitting CFI to both sections by directive: .cfi_sections >> .debug_frame,.eh_frame >> >> At the same time gcc for arm emits CFI in both debug_frame and .ARM.exidx >> >> I'm aware about CFI for Exception Handling. But what the reason to not >> emit both ? >> Is there any implicit reason for that or it's just a bug ? On Arm, the .ARM.exidx data is insufficient for debugging, so we certainly need the additional information in the dwarf unwinding tables. On AArch64 that's not true, the information is complete enough for a debugger to use. So I presume this is done to avoid wasting space with duplicate information. What do other targets that use dwarf exception unwinding do? R. >> >> Steps to reproduce: >> >> cat > test.cpp <<EOF >> int foo() { >> return 0; >> } >> EOF >> >> ./aarch64-none-elf-gcc -c -g test.cpp -o test_cpp.o && >> ./aarch64-none-elf-objdump -g test_cpp.o | grep -B 3 "CIE" | grep >> "_frame" >> Contents of the .eh_frame section: >> >> While for C code it does: >> cat > test.c <<EOF >> int foo() { >> return 0; >> } >> EOF >> >> ./aarch64-none-elf-gcc -c -g test.c -o test_c.o && >> ./aarch64-none-elf-objdump -g test_c.o | grep -B 3 "CIE" | grep >> "_frame" >> Contents of the .debug_frame section: >> >> >> Alex >
