End the output capture when a test exits, fail on missing reports

A test that called exit() crashed its worker with SIGSEGV on Linux and
macOS. The exit hook read Catch2's captured output through a scoped
deactivation, which switched the capture back on; libstdc++ then flushed
std::cout at exit into a capture buffer that static destruction had
already freed. RunContext::endCapture() now ends the capture for good and
returns what it held, so the standard streams are their own again.

A JUnit, JSON or trace report that could not be written was only
reported on stderr, and a run whose tests passed still exited with 0, so a
build server could miss it. Such a run now exits with 1; failed tests
still exit with 42.

Integration tests of the runner's output move their helpers into
RunnerFixtureClient.hpp and cover --version, --help, the listing modes, a
bad option, exit codes 1 to 4, -v, -q, --slowest, colours, --analytics
in text and JSON, and Bazel's test environment.

2 files changed, 8 insertions, 5 deletions

diff --git a/src/catch2/internal/catch_run_context.cpp b/src/catch2/internal/catch_run_context.cpp
index 5c57ef18..30fa3edd 100644
--- a/src/catch2/internal/catch_run_context.cpp
+++ b/src/catch2/internal/catch_run_context.cpp
@@ -748,11 +748,11 @@ namespace Catch {
         return m_atomicAssertionCount.failed >= m_abortAfterXFailedAssertions;
     }
 
-    std::string RunContext::capturedOutput() {
+    std::string RunContext::endCapture() {
         if ( !m_outputRedirect->isActive() ) {
             return {};
         }
-        auto _ = scopedDeactivate( *m_outputRedirect );
+        m_outputRedirect->deactivate();
         return m_outputRedirect->getStdout() + m_outputRedirect->getStderr();
     }
 
diff --git a/src/catch2/internal/catch_run_context.hpp b/src/catch2/internal/catch_run_context.hpp
index c7bee285..5feb8890 100644
--- a/src/catch2/internal/catch_run_context.hpp
+++ b/src/catch2/internal/catch_run_context.hpp
@@ -106,9 +106,12 @@ namespace Catch {
         // !TBD We need to do this another way!
         bool aborting() const;
 
-        //! What the running test printed so far and was captured; for a
-        //! process that ends inside a test, whose end is never reported.
-        std::string capturedOutput();
+        //! Ends the capture of the running test's output and returns what
+        //! it captured; for a process that ends inside a test, whose end is
+        //! never reported. The standard streams are their own again, so
+        //! flushing them at exit no longer reaches the capture buffers,
+        //! which may be gone by then.
+        std::string endCapture();
 
     private:
         void assertionPassedFastPath( SourceLineInfo lineInfo );