Capture std::clog writes and combine them with std::cerr writes (#989)

This also introduces Catch::clog() method to allow embedded targets
to override std::clog usage with their own stream (presumably null-sink),
similarly to how Catch::cout() and Catch::cerr() are used.

Fixes #989

include/internal/catch_run_context.hpp

@@ -22,6 +22,7 @@
 #include "catch_result_builder.h"
 #include "catch_fatal_condition.hpp"
 
+
 #include <set>
 #include <string>
 
@@ -50,6 +51,29 @@ namespace Catch {
         std::string& m_targetString;
     };
 
+    // StdErr has two constituent streams in C++, std::cerr and std::clog
+    // This means that we need to redirect 2 streams into 1 to keep proper
+    // order of writes and cannot use StreamRedirect on its own
+    class StdErrRedirect {
+    public:
+        StdErrRedirect(std::string& targetString)
+        :m_cerrBuf( cerr().rdbuf() ), m_clogBuf(clog().rdbuf()),
+        m_targetString(targetString){
+            cerr().rdbuf(m_oss.rdbuf());
+            clog().rdbuf(m_oss.rdbuf());
+        }
+        ~StdErrRedirect() {
+            m_targetString += m_oss.str();
+            cerr().rdbuf(m_cerrBuf);
+            clog().rdbuf(m_clogBuf);
+        }
+    private:
+        std::streambuf* m_cerrBuf;
+        std::streambuf* m_clogBuf;
+        std::ostringstream m_oss;
+        std::string& m_targetString;
+    };
+
     ///////////////////////////////////////////////////////////////////////////
 
     class RunContext : public IResultCapture, public IRunner {
@@ -305,7 +329,7 @@ namespace Catch {
                 timer.start();
                 if( m_reporter->getPreferences().shouldRedirectStdOut ) {
                     StreamRedirect coutRedir( Catch::cout(), redirectedCout );
-                    StreamRedirect cerrRedir( Catch::cerr(), redirectedCerr );
+                    StdErrRedirect errRedir( redirectedCerr );
                     invokeActiveTestCase();
                 }
                 else {

include/internal/catch_stream.h

@@ -21,6 +21,7 @@ namespace Catch {
 
     std::ostream& cout();
     std::ostream& cerr();
+    std::ostream& clog();
 
 
     struct IStream {

include/internal/catch_stream.hpp

@@ -103,6 +103,9 @@ namespace Catch {
     std::ostream& cerr() {
         return std::cerr;
     }
+    std::ostream& clog() {
+        return std::clog;
+    }
 #endif
 }
 

projects/SelfTest/Baselines/console.std.approved.txt

@@ -622,6 +622,9 @@ with messages:
 
 A string sent directly to stdout
 A string sent directly to stderr
+Write to std::cerr
+Write to std::clog
+Interleaved writes to error streams
 Message from section one
 Message from section two
 -------------------------------------------------------------------------------
@@ -953,6 +956,6 @@ with expansion:
   "first" == "second"
 
 ===============================================================================
-test cases: 168 | 119 passed | 45 failed |  4 failed as expected
+test cases: 169 | 120 passed | 45 failed |  4 failed as expected
 assertions: 968 | 859 passed | 88 failed | 21 failed as expected
 

projects/SelfTest/Baselines/console.sw.approved.txt

@@ -6786,6 +6786,39 @@ PASSED:
 with expansion:
   Approx( 1.23 ) != 1.24
 
+Write to std::cerr
+-------------------------------------------------------------------------------
+Standard error is reported and redirected
+  std::cerr
+-------------------------------------------------------------------------------
+MessageTests.cpp:<line number>
+...............................................................................
+
+
+No assertions in section 'std::cerr'
+
+Write to std::clog
+-------------------------------------------------------------------------------
+Standard error is reported and redirected
+  std::clog
+-------------------------------------------------------------------------------
+MessageTests.cpp:<line number>
+...............................................................................
+
+
+No assertions in section 'std::clog'
+
+Interleaved writes to error streams
+-------------------------------------------------------------------------------
+Standard error is reported and redirected
+  Interleaved writes to cerr and clog
+-------------------------------------------------------------------------------
+MessageTests.cpp:<line number>
+...............................................................................
+
+
+No assertions in section 'Interleaved writes to cerr and clog'
+
 Message from section one
 -------------------------------------------------------------------------------
 Standard output from all sections is reported
@@ -9483,6 +9516,6 @@ MiscTests.cpp:<line number>:
 PASSED:
 
 ===============================================================================
-test cases: 168 | 118 passed | 46 failed |  4 failed as expected
+test cases: 169 | 118 passed | 47 failed |  4 failed as expected
-assertions: 970 | 859 passed | 90 failed | 21 failed as expected
+assertions: 973 | 859 passed | 93 failed | 21 failed as expected
 

projects/SelfTest/Baselines/junit.sw.approved.txt

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <testsuitesspanner>
-  <testsuite name="<exe-name>" errors="13" failures="78" tests="971" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
+  <testsuite name="<exe-name>" errors="13" failures="81" tests="974" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
     <testcase classname="global" name="# A test name that starts with a #" time="{duration}"/>
     <testcase classname="#748 - captures with unexpected exceptions" name="outside assertions" time="{duration}">
       <error type="TEST_CASE">
@@ -475,6 +475,13 @@ A string sent directly to stderr
       </system-err>
     </testcase>
     <testcase classname="global" name="Some simple comparisons between doubles" time="{duration}"/>
+    <testcase classname="Standard error is reported and redirected" name="Interleaved writes to cerr and clog" time="{duration}">
+      <system-err>
+Write to std::cerr
+Write to std::clog
+Interleaved writes to error streams
+      </system-err>
+    </testcase>
     <testcase classname="Standard output from all sections is reported" name="two" time="{duration}">
       <system-out>
 Message from section one
@@ -750,6 +757,9 @@ hello
     </system-out>
     <system-err>
 A string sent directly to stderr
+Write to std::cerr
+Write to std::clog
+Interleaved writes to error streams
     </system-err>
   </testsuite>
 </testsuites>

projects/SelfTest/Baselines/xml.sw.approved.txt

@@ -7309,6 +7309,24 @@ A string sent directly to stderr
       </Expression>
       <OverallResult success="true"/>
     </TestCase>
+    <TestCase name="Standard error is reported and redirected" tags="[.][hide][messages]" filename="projects/<exe-name>/MessageTests.cpp" >
+      <Section name="std::cerr" filename="projects/<exe-name>/MessageTests.cpp" >
+        <OverallResults successes="0" failures="1" expectedFailures="0"/>
+      </Section>
+      <Section name="std::clog" filename="projects/<exe-name>/MessageTests.cpp" >
+        <OverallResults successes="0" failures="1" expectedFailures="0"/>
+      </Section>
+      <Section name="Interleaved writes to cerr and clog" filename="projects/<exe-name>/MessageTests.cpp" >
+        <OverallResults successes="0" failures="1" expectedFailures="0"/>
+      </Section>
+      <OverallResult success="false">
+        <StdErr>
+Write to std::cerr
+Write to std::clog
+Interleaved writes to error streams
+        </StdErr>
+      </OverallResult>
+    </TestCase>
     <TestCase name="Standard output from all sections is reported" tags="[.][hide][messages]" filename="projects/<exe-name>/MessageTests.cpp" >
       <Section name="one" filename="projects/<exe-name>/MessageTests.cpp" >
         <OverallResults successes="0" failures="1" expectedFailures="0"/>
@@ -10143,7 +10161,7 @@ spanner      <OverallResult success="true"/>
       </Section>
       <OverallResult success="true"/>
     </TestCase>
-    <OverallResults successes="859" failures="91" expectedFailures="21"/>
+    <OverallResults successes="859" failures="94" expectedFailures="21"/>
   </Group>
-  <OverallResults successes="859" failures="90" expectedFailures="21"/>
+  <OverallResults successes="859" failures="93" expectedFailures="21"/>
 </Catch>

projects/SelfTest/MessageTests.cpp

@@ -99,6 +99,23 @@ TEST_CASE( "Standard output from all sections is reported", "[messages][.]" )
     }
 }
 
+TEST_CASE( "Standard error is reported and redirected", "[messages][.]" ) {
+    SECTION( "std::cerr" ) {
+        std::cerr << "Write to std::cerr" << std::endl;
+    }
+    SECTION( "std::clog" ) {
+        std::clog << "Write to std::clog" << std::endl;
+    }
+    SECTION( "Interleaved writes to cerr and clog" ) {
+        std::cerr << "Inter";
+        std::clog << "leaved";
+        std::cerr << ' ';
+        std::clog << "writes";
+        std::cerr << " to error";
+        std::clog << " streams\n";
+    }
+}
+
 TEST_CASE( "SCOPED_INFO is reset for each loop", "[messages][failing][.]" )
 {
     for( int i=0; i<100; i++ )