lcov usage fails with clang #12602

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When attempting to generate coverage information with make cov after configuring and building with clang, lcov/gcov (for the versions I'm using) are unable to parse the generated gcda files:

/home/james/tmp/bitcoin/src/libbitcoin_server_a-miner.gcno:version '402*', prefer 'A72*'
geninfo: ERROR: GCOV failed for /home/james/tmp/bitcoin/src/libbitcoin_server_a-miner.gcda!
Makefile:1269: recipe for target 'test_bitcoin.info' failed

We may need to special-case the effects of --enable-lcov when building with clang to use flags and commands mentioned here.

Configure output

Options used to compile and link:
  with wallet   = yes
  with gui / qt = yes
    qt version  = 5
    with qr     = auto
  with zmq      = yes
  with test     = yes
  with bench    = yes
  with upnp     = auto
  use asm       = yes
  debug enabled = no
  werror        = no

  target os     = linux
  build os      =

  CC            = /usr/bin/clang-4.0
  CFLAGS        = -g -O2
  CPPFLAGS      = -I/home/james/tmp/bitcoin/db4/include/ -DHAVE_BUILD_INFO -D__STDC_FORMAT_MACROS
  CXX           = /usr/bin/clang++-4.0 -std=c++11
  CXXFLAGS      = -std=c++11 -std=c++11  --coverage -Og
  LDFLAGS       = -L/home/james/tmp/bitcoin/db4/lib/ --coverage
  ARFLAGS       = cr

Versions

 $ clang++-4.0 --version

clang version 4.0.1-6 (tags/RELEASE_401/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

 $ lcov --version

lcov: LCOV version 1.13

 $ gcov --version

gcov (Ubuntu 7.2.0-8ubuntu3.2) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.

make cov failure

$ make cov
...
/usr/bin/lcov --gcov-tool=/usr/bin/gcov -c  -d /home/james/tmp/bitcoin/src -t test_bitcoin -o test_bitcoin.info
Capturing coverage data from /home/james/tmp/bitcoin/src
Found gcov version: 7.2.0
Scanning /home/james/tmp/bitcoin/src for .gcda files ...
Found 290 data files in /home/james/tmp/bitcoin/src
Processing src/libbitcoin_server_a-miner.gcda
/home/james/tmp/bitcoin/src/libbitcoin_server_a-miner.gcno:version '402*', prefer 'A72*'
geninfo: ERROR: GCOV failed for /home/james/tmp/bitcoin/src/libbitcoin_server_a-miner.gcda!
Makefile:1269: recipe for target 'test_bitcoin.info' failed
make: *** [test_bitcoin.info] Error 29
rm test_bitcoin.info baseline_filtered.info baseline.info

I always assumed that gcov only works with gcc.

Might preferable to warn during configuration if --enable-coverage is combined with non-gcc usage. I'll try for a PR soonish.

I'd rather add support for llvm-cov in addition to --enable-lcov

You can use llvm-cov with clang with the following diff applied:

diff --git a/configure.ac b/configure.ac
index 2c648b0b5c..c502543a1a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -87,7 +87,7 @@ dnl Check/return PATH for base programs.
 AC_PATH_TOOL(AR, ar)
 AC_PATH_TOOL(RANLIB, ranlib)
 AC_PATH_TOOL(STRIP, strip)
-AC_PATH_TOOL(GCOV, gcov)
+AC_PATH_TOOL(GCOV, llvm-cov_gcov)
 AC_PATH_PROG(LCOV, lcov)
 dnl Python 3.5 is specified in .python-version and should be used if available, see doc/dependencies.md
 AC_PATH_PROGS([PYTHON], [python3.5 python3.6 python3.7 python3.8 python3 python])

Then create an executable file

$ cat ~/bin/llvm-cov_gcov 
#!/usr/bin/env bash
exec llvm-cov gcov "$@"
$ which llvm-cov_gcov
~/bin/llvm-cov_gcov