mark inline functions containing static members as hidden (#779)

* inline functions w/static members should be hidden

* update NEWS

NEWS.md

@@ -12,6 +12,10 @@
 
 ## Minor improvements and bug fixes
 
+* Fixed an issue where `devtools::test()` could fail if run multiple times
+  within the same R session for a package containing Catch tests.
+  ([devtools #1832](https://github.com/r-lib/devtools/issues/1832))
+
 * `testing_package()` function added to retrieve the name of the package
   currently being tested (#699).
 

inst/include/testthat/testthat.h

@@ -12,9 +12,16 @@
  * Force 'testthat' to be disabled by defining TESTTHAT_DISABLED.
  * TESTTHAT_DISABLED takes precedence.
  * 'testthat' is disabled on Solaris by default.
+ *
+ * Hide symbols containing static members on gcc, to work around issues
+ * with DLL unload due to static members in inline functions.
+ * https://github.com/r-lib/devtools/issues/1832
  */
 #if defined(__GNUC__) || defined(__clang__)
 # define TESTTHAT_ENABLED
+# define TESTTHAT_ATTRIBUTE_HIDDEN __attribute__ ((visibility("hidden")))
+#else
+# define TESTTHAT_ATTRIBUTE_HIDDEN
 #endif
 
 #if defined(__SUNPRO_C) || defined(__SUNPRO_CC) || defined(__sun) || defined(__SVR4)
@@ -107,6 +114,7 @@ class r_ostream : public std::ostream {
 // exported by testthat.
 # ifdef CATCH_CONFIG_RUNNER
 
+TESTTHAT_ATTRIBUTE_HIDDEN
 inline Catch::Session& catchSession()
 {
   static Catch::Session instance;
@@ -124,12 +132,14 @@ inline bool run_tests()
 
 namespace Catch {
 
+TESTTHAT_ATTRIBUTE_HIDDEN
 inline std::ostream& cout()
 {
   static testthat::r_ostream instance;
   return instance;
 }
 
+TESTTHAT_ATTRIBUTE_HIDDEN
 inline std::ostream& cerr()
 {
   static testthat::r_ostream instance;