Segfault bootstrapping on aarch64

[markos]

After bootstrapping successfully from the latest ltsmaster on debian/arm64 (unstable), I tried to build the latest 1.1.0+b6 package. Tried with both llvm-3.8 (default for the package) and llvm-3.9 (in case it contained fixes for arm64), bootstrap fails eventually at this point:

# cd /root/ldc-1.1.0+b6 && /root/ldc-1.1.0+b6/build-static/bin/ldc2 --output-o -c -I/root/ldc-1.1.0+b6/runtime/druntime/src -I/root/ldc-1.1.0+b6/runtime/druntime/src/gc /root/ldc-1.1.0+b6/runtime/phobos/std/array.d -of/root/ldc-1.1.0+b6/build-static/runtime/std/array-debug.o -g -link-debuglib -I/root/ldc-1.1.0+b6/runtime/phobos -v-cg
0  libLLVM-3.9.so.1 0x0000ffff7f580f44 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 52
Segmentation fault
root@sirius:~/ldc-1.1.0+b6# gdb /root/ldc-1.1.0+b6/build-static/bin/ldc2
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and "show warranty" for details.
This GDB was configured as "aarch64-linux-gnu".
Type "show configuration" for configuration details.
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Reading symbols from /root/ldc-1.1.0+b6/build-static/bin/ldc2...done.
(gdb) run --output-o -c -I/root/ldc-1.1.0+b6/runtime/druntime/src -I/root/ldc-1.1.0+b6/runtime/druntime/src/gc /root/ldc-1.1.0+b6/runtime/phobos/std/array.d -of/root/ldc-1.1.0+b6/build-static/runtime/std/array-debug.o -g -link-debuglib -I/root/ldc-1.1.0+b6/runtime/phobos
Starting program: /root/ldc-1.1.0+b6/build-static/bin/ldc2 --output-o -c -I/root/ldc-1.1.0+b6/runtime/druntime/src -I/root/ldc-1.1.0+b6/runtime/druntime/src/gc /root/ldc-1.1.0+b6/runtime/phobos/std/array.d -of/root/ldc-1.1.0+b6/build-static/runtime/std/array-debug.o -g -link-debuglib -I/root/ldc-1.1.0+b6/runtime/phobos
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
_IO_vsnprintf (string=0xaaaaab009360 "", maxlen=<optimized out>, format=0xaaaaaae92157 "__unittestL%u_", args=<error reading variable: Cannot access memory at address 0x111>) at vsnprintf.c:114
114	vsnprintf.c: No such file or directory.
(gdb) where
#0  _IO_vsnprintf (string=0xaaaaab009360 "", maxlen=<optimized out>, format=0xaaaaaae92157 "__unittestL%u_", args=<error reading variable: Cannot access memory at address 0x111>) at vsnprintf.c:114
#1  0x0000aaaaaacbf248 in OutBuffer::vprintf(char const*, std::__va_list) ()
#2  0x0000aaaaaac389bc in OutBuffer::printf(char const*, ...) ()
#3  0x0000aaaaaad0bd40 in unitTestId(Loc) ()
#4  0x0000aaaaaac263c0 in ddmd.parse.Parser.parseDeclDefs(int, ddmd.dsymbol.Dsymbol*, ddmd.parse.PrefixAttributes*) ()
#5  0x0000aaaaaac2538c in ddmd.parse.Parser.parseDeclDefs(int, ddmd.dsymbol.Dsymbol*, ddmd.parse.PrefixAttributes*) ()
#6  0x0000aaaaaac2538c in ddmd.parse.Parser.parseDeclDefs(int, ddmd.dsymbol.Dsymbol*, ddmd.parse.PrefixAttributes*) ()
#7  0x0000aaaaaac2538c in ddmd.parse.Parser.parseDeclDefs(int, ddmd.dsymbol.Dsymbol*, ddmd.parse.PrefixAttributes*) ()
#8  0x0000aaaaaac93008 in ddmd.parse.Parser.parseModule() ()
#9  0x0000aaaaaac916cc in Module::parse() ()
#10 0x0000aaaaaad302e8 in mars_mainBody(Array<char const*>&, Array<char const*>&) ()
#11 0x0000aaaaaae2d49c in cppmain (argc=<optimized out>, argv=<optimized out>) at ./driver/main.cpp:1101
#12 0x0000aaaaaae77dac in rt.dmain2._d_run_main(int, char**, extern(C) int(char[][]) function).runAll().__lambda1() ()
#13 0x0000aaaaaae77d64 in rt.dmain2._d_run_main(int, char**, extern(C) int(char[][]) function).tryExec(scope void() delegate) ()
#14 0x0000aaaaaae77c68 in _d_run_main ()
#15 0x0000ffffb5506364 in __libc_start_main (main=0x0, argc=0, argv=0x0, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=<optimized out>) at libc-start.c:291
#16 0x0000aaaaaabf4238 in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

[kinke]

varargs - https://github.com/ldc-developers/druntime/blob/ldc/src/core/stdc/stdarg.d looks incomplete for AArch64. Not really surprising, as the only LDC dev working on that platform (Kai) is currently blocked from LDC development.

[markos]

Any suggestions on how/what to fix?

[kinke]

Most of it should be in that file, some adaptations might also be required in https://github.com/ldc-developers/ldc/blob/master/gen/abi-aarch64.cpp. Running the dmd-testsuite tests (ctest -R dmd-testsuite-debug in the CMake working dir) should help as there are multiple ABI tests in there, some of which involve variadics. And some docs about the AArch64 ABI details or at least a C++ stdarg.h header won't hurt either.

[joakim-noah]

Should finally work with latest releases 0.17.6/1.11.0, let us know if it doesn't.