https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101996
Bug ID: 101996
Summary: libatomic: RISC-V 64: Infinite recursion in
__atomic_compare_exchange_1
Product: gcc
Version: 10.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: bqq3z3afgj at bcco4 dot anonbox.net
Target Milestone: ---
On Alpine Linux Edge, we noticed a stack overflow in
__atomic_compare_exchange_1 in libatomic.so. The generated RV64
assembler for the __atomic_compare_exchange_1 symbol looks as follows:
0000000000001e40 <__atomic_compare_exchange_1@plt>:
1e40: 00003e17 auipc t3,0x3
1e44: 2a0e3e03 ld t3,672(t3) # 50e0
<__atomic_compare_exchange_1+0x2312>
1e48: 000e0367 jalr t1,t3
1e4c: 00000013 nop
0000000000002dce <__atomic_compare_exchange_1>:
2dce: 1141 addi sp,sp,-16
2dd0: 4701 li a4,0
2dd2: 4695 li a3,5
2dd4: e406 sd ra,8(sp)
2dd6: 86aff0ef jal ra,1e40
<__atomic_compare_exchange_1@plt>
2dda: 60a2 ld ra,8(sp)
2ddc: 0141 addi sp,sp,16
2dde: 8082 ret
It seems to me that __atomic_compare_exchange_1 calls itself recursively
via __atomic_compare_exchange_1@plt each time adding a new stackframe in
2dce, 2ddc (which pops the stack frame) is never reached due to the
recursive invocation in 2dd6. Thus ultimatly causing a stack overflow.
One theory on the #gcc IRC was that riscv claims to have atomic_*
builtins but ends up not generating them thus causing the infinite
recursion.
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/riscv64-alpine-linux-musl/10.3.1/lto-wrapper
Target: riscv64-alpine-linux-musl
Configured with:
/home/buildozer/aports-dev/main/gcc/src/gcc-10.3.1_git20210625/configure
--prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info
--build=riscv64-alpine-linux-musl --host=riscv64-alpine-linux-musl
--target=riscv64-alpine-linux-musl --with-pkgversion='Alpine
10.3.1_git20210625' --enable-checking=release --disable-fixed-point
--disable-libstdcxx-pch --disable-multilib --disable-nls --disable-werror
--disable-symvers --enable-__cxa_atexit --enable-default-pie
--enable-default-ssp --enable-cloog-backend
--enable-languages=c,c++,objc,go,fortran --with-arch=rv64gc --with-abi=lp64d
--enable-autolink-libatomic --disable-libquadmath --disable-libssp
--disable-libmpx --disable-libmudflap --disable-libsanitizer --enable-shared
--enable-threads --enable-tls --disable-libitm --with-system-zlib
--with-linker-hash-style=gnu
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.3.1 20210625 (Alpine 10.3.1_git20210625)
Downstream bug report:
https://gitlab.alpinelinux.org/alpine/aports/-/issues/12817
