Compilation failure with `-O0` + `-fsanitize=address` due to inline asm #29801

Is there an existing issue for this?

• I have searched the existing issues

Current behaviour

Configure with

./configure --enable-fuzz --enable-debug --with-sanitizers=address,fuzzer,undefined,integer CC=clang CXX=clang++

Compile fails:

crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:1882: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:2591: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:3284: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:4686: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:5395: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:6088: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:7490: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:8199: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:8892: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:10312: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:11021: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:11714: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:12859: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:13356: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:13853: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:14900: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:15397: note: instantiated into assembly here
crypto/sha256_sse4.cpp:44:9: error: expected relocatable expression
   44 |         "shl    $0x6,%2;"
      |         ^
<inline asm>:1:15894: note: instantiated into assembly here
18 errors generated.
make[2]: *** [Makefile:14531: crypto/libbitcoin_crypto_base_la-sha256_sse4.lo] Error 1

Expected behaviour

It should successfully compile with the debug symbols so that fuzz crashes can be debugged.

Previously, it was possible to work around this issue by using --disable-asm however that was removed in #29407

Steps to reproduce

See above configure .

--enable-debug and --enable-fuzz individually do not result in compilation failure. I am only seeing this when using them together.

Relevant log output

config.log

How did you obtain Bitcoin Core

Compiled from source

What version of Bitcoin Core are you using?

master@0d509bab45d292caeaf34600e57b5928757c6005

Operating system and version

Arch w/ linux kernel 6.8.2

Machine specifications

No response

Recalling the IRC discussion, I presume this happens since -O0 in #16435 ?

Ref:

1802024-04-01T18:09:22  <cfields> clang++ -std=c++20 -O0 -fsanitize=address -c crypto/sha256_sse4.cpp -o out.o

https://www.erisian.com.au/bitcoin-core-dev/log-2024-04-02.html

The broken combination is clang++ -std=c++20 -O0 -fsanitize=address -c crypto/sha256_sse4.cpp -o out.o, pointed out by Cory. Happens for me with Clang-18.

I guess the next step is to followup / file an issue with LLVM. I've got #29796 open which may "fix" this by just dropping -O0, depending on the outcome of discussion.

FWIW, unable to reproduce on arm64 macOS 14.4.1 with Homebrew clang 17.0.6.

It only happens on x86-64, because the asm is in that format.

In addition to the discussion in #29781, I'll PR a change to make this work with DISABLE_OPTIMIZED_SHA256 as a fallback. I'm doing that as part of a larger refactor of the crypto defines, though.

How about adding something like:

--- a/configure.ac
+++ b/configure.ac
@@ -349,7 +349,14 @@ esac
 if test "$enable_debug" = "yes"; then
 
   dnl Disable all optimizations
-  AX_CHECK_COMPILE_FLAG([-O0], [DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -O0"], [], [$CXXFLAG_WERROR])
+  case "$use_sanitizers" in
+    *address*)
+      AX_CHECK_COMPILE_FLAG([-Og], [DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -Og"], [], [$CXXFLAG_WERROR])
+      ;;
+    *)
+      AX_CHECK_COMPILE_FLAG([-O0], [DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -O0"], [], [$CXXFLAG_WERROR])
+      ;;
+  esac

in the meantime?

@ajtowns Thanks for the reminder here. See #30097 for a function-level application (kinda :) of the above.