Merge branch 'master' into traceback-doc

CONTRIBUTING.md

@@ -47,7 +47,18 @@ Flag                  | Effect
 ./run-tests -k        | Run all tests even if some tests are failing
 ./run-tests -o gtest  | The gtest output format might be easier to read if you are using print statements for debugging.
 
-For convenience, when the test script is run without any parameters, it also runs the linter at the end.
+For convenience, when the test script is run without any busted parameters, it also runs the linter at the end.
+
+#### Testing garbage collection
+
+Doing proper GC testing takes longer, so we have a special mode for doing that.
+For testing garbage collection more carefully, set the `EXTRACFLAGS`
+environment variable to "-DHARDMEMTESTS" for the `run-tests` script. For
+example:
+
+```sh
+$ EXTRACFLAGS="-DHARDMEMTESTS" ./run-tests
+```
 
 ### Running the benchmarks suite
 

run-tests

@@ -1,6 +1,7 @@
 #!/bin/bash
 
-# HOW TO USE: This is a wrapper around busted. The command-line arguments are the same.
+# HOW TO USE: This is a wrapper around busted. Pass "gc" as the first argument for testing the
+# garbage collector. Except for "gc", the command-line arguments are the same of busted
 #
 # EXAMPLES:
 #   ./run-tests
@@ -19,7 +20,7 @@ FLAGS=(--verbose --no-keep-going)
 
 # To speed things up, we tell the C compiler to skip optimizations. (It's OK, the CI still uses -O2)
 # Also, add some compiler flags to verify standard compliance.
-export CFLAGS='-O0 -std=c99 -Wall -Werror -Wundef -Wno-unused'
+export CFLAGS="-O0 -std=c99 -Wall -Werror -Wundef -Wno-unused $EXTRACFLAGS"
 
 if [ "$#" -eq 0 ]; then
     if command -v parallel >/dev/null; then