Keep per-test coverage with --coverage (roadmap step 4)feature/per-test-coverage

--coverage=DIR runs every attempt in a process of its own and keeps the
coverage of each test, for binaries built with LLVM source-based
coverage (Clang: -fprofile-instr-generate -fcoverage-mapping) or gcov
(GCC: --coverage).

How it works:

- The scheduler gives each attempt a fresh worker, as --isolate does,
  and sets LLVM_PROFILE_FILE and GCOV_PREFIX for it: the profile the
  process writes at exit is then the coverage of that one test, in
  DIR/profiles/t<index>-a<attempt>.profraw or a .gcov directory. Each
  runtime reads its own variable, so no symbol of either runtime is
  looked up: weak references would not pull them out of their static
  archives, and Mach-O does not allow undefined weak symbols.
- A process that runs other tests first (bisection) writes beside the
  profiles, never into one. The attempt records its profile, also in
  the JSON results.
- The profiles of an earlier run are removed when the run starts,
  because gcov adds to the .gcda files it finds.
- After the run, CoverageReport reads the last profile of every test:
  llvm-profdata and llvm-cov (PATH, xcrun on macOS, or
  CATCH3_LLVM_PROFDATA / CATCH3_LLVM_COV) export LCOV, gcov (or
  CATCH3_GCOV) writes JSON next to a copy of the .gcno. The result is
  DIR/coverage.json, the files, lines and branches each test reached,
  and DIR/coverage.lcov for the whole run. Without the tools the
  profiles stay and the run says so.
- --coverage with --in-process or --break is refused.

Tests: option parsing, LCOV reading and writing, gcov JSON, and an
integration test on CoverageFixture, a binary CMake builds with the
coverage flags of Clang or GCC: two tests reach different lines, each
map holds only its own, the LCOV report holds both, and a stale profile
of an earlier run is gone. Locally all 84 CTest tests pass with Clang,
and the coverage tests pass with GCC (built with
CATCH3_ENABLE_WERROR=OFF: Catch3 does not build with GCC's warnings as
errors, before and after this change).

CI: the Linux jobs install LLVM's coverage tools, a new job checks the
gcov path with GCC, and CATCH3_COVERAGE_REQUIRE_MAP turns a missing map
into a failure on Linux and macOS instead of a skip. MSVC has no
source-based coverage, so its builds skip those tests; the roadmap
lists step 4 as in progress until Windows with clang-cl is tested.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/Progmasoft/Runner/Runner.cpp b/src/Progmasoft/Runner/Runner.cpp
index 77011322..61f8f2b7 100644
--- a/src/Progmasoft/Runner/Runner.cpp
+++ b/src/Progmasoft/Runner/Runner.cpp
@@ -22,6 +22,7 @@
 #include <random>
 #include <system_error>
 
+#include "CoverageReport.hpp"
 #include "Analysis.hpp"
 #include "Catalog.hpp"
 #include "Console.hpp"
@@ -949,6 +950,17 @@ namespace Progmasoft::Catch3
                 }
             }
 
+            if (!options.coverageDirectory.empty())
+            {
+                if (auto status = Runner::PrepareCoverageDirectory(
+                        options.coverageDirectory);
+                    !status)
+                {
+                    PrintError(status.GetError().Message());
+                    return Catch::UnspecifiedErrorExitCode;
+                }
+            }
+
             const auto started = std::chrono::steady_clock::now();
             RunResult run;
             run.binary = programName;
@@ -983,6 +995,14 @@ namespace Progmasoft::Catch3
                 run.tests.push_back(std::move(kept));
             }
             run.notes = std::move(outcome.notes);
+            if (!options.coverageDirectory.empty())
+            {
+                for (auto &note : Runner::WriteCoverageReports(
+                         options.coverageDirectory, run, program.string()))
+                {
+                    run.notes.push_back(std::move(note));
+                }
+            }
 
             const bool anyFailure
                 = std::any_of(run.tests.begin(),