Improving detection of garbage collection bugs

CONTRIBUTING.md

@@ -47,7 +47,19 @@ 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, pass "gc" as the first parameter
+of the script. The rest of the parameters will do the same as before:
+
+```sh
+$ ./run-tests gc                       # Run all tests but with proper GC testing
+$ ./run-tests gc spec/parser_spec.lua  # Run just one of the test suite files
+                                       # but with proper GC testing
+```
 
 ### Running the benchmarks suite
 

run-tests

@@ -1,11 +1,17 @@
 #!/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
 #   ./run-tests -k
 #   ./run-tests spec/coder_spec.lua
+#   ./run-tests gc
+#   ./run-tests gc -k
+
+test_gc=""
+[ "$1" = "gc" ] && test_gc="y" && shift
 
 echo "--- Test Suite ---"
 
@@ -21,6 +27,11 @@ FLAGS=(--verbose --no-keep-going)
 # Also, add some compiler flags to verify standard compliance.
 export CFLAGS='-O0 -std=c99 -Wall -Werror -Wundef -Wpedantic -Wno-unused'
 
+# When testing the garbage collector, we use -O2 for a greater chance of finding bugs.
+# The HARDMEMTESTS macro makes lualib do garbage collection whenever it can.
+[ -n "$test_gc" ] &&
+    CFLAGS='-DHARDMEMTESTS -O2 -std=c99 -Wall -Werror -Wundef -Wpedantic -Wno-unused'
+
 if [ "$#" -eq 0 ]; then
     if command -v parallel >/dev/null; then
         parallel busted -o utfTerminal "${FLAGS[@]}" ::: spec/*_spec.lua