Adding GC: MMTk tag to Julia's banner when building with MMTk (#72)

* Adding GC: MMTk tag to banner when running with MMTk

* Getting info about MMTk build and printing it out

* Fixing whitespace

Author: udesou

src/gc-interface.h

@@ -100,6 +100,8 @@ JL_DLLEXPORT void jl_gc_collect(jl_gc_collection_t collection);
 JL_DLLEXPORT int gc_is_collector_thread(int tid) JL_NOTSAFEPOINT;
 // Pinning objects; Returns whether the object has been pinned by this call.
 JL_DLLEXPORT unsigned char jl_gc_pin_object(void* obj);
+// Returns the version of which GC implementation is being used according to the list of supported GCs
+JL_DLLEXPORT const char* jl_active_gc_impl(void);
 
 // ========================================================================= //
 // Metrics

src/gc-mmtk.c

@@ -310,6 +310,11 @@ JL_DLLEXPORT unsigned char jl_gc_pin_object(void* obj) {
 // GC Statistics
 // ========================================================================= //
 
+JL_DLLEXPORT const char* jl_active_gc_impl(void) {
+    const char* mmtk_version = get_mmtk_version();
+    return mmtk_version;
+}
+
 int64_t last_gc_total_bytes = 0;
 int64_t last_live_bytes = 0; // live_bytes at last collection
 int64_t live_bytes = 0;

src/gc-stock.c

@@ -4000,6 +4000,10 @@ JL_DLLEXPORT void jl_gc_wb2_slow(const void *parent, const void* ptr) JL_NOTSAFE
 {
 }
 
+JL_DLLEXPORT const char* jl_active_gc_impl(void) {
+    return "";
+}
+
 #ifdef __cplusplus
 }
 #endif

stdlib/REPL/src/REPL.jl

@@ -1771,6 +1771,8 @@ function banner(io::IO = stdout; short = false)
         end
     end
 
+    gc_version = unsafe_string(ccall(:jl_active_gc_impl, Ptr{UInt8}, ()))
+
     commit_date = isempty(Base.GIT_VERSION_INFO.date_string) ? "" : " ($(split(Base.GIT_VERSION_INFO.date_string)[1]))"
 
     if get(io, :color, false)::Bool
@@ -1784,7 +1786,7 @@ function banner(io::IO = stdout; short = false)
 
         if short
             print(io,"""
-              $(d3)o$(tx)  | Version $(VERSION)$(commit_date)
+              $(d3)o$(tx)  | Version $(VERSION)$(commit_date) $(gc_version)
              $(d2)o$(tx) $(d4)o$(tx) | $(commit_string)
             """)
         else
@@ -1795,14 +1797,14 @@ function banner(io::IO = stdout; short = false)
               $(jl)| | | | | | |/ _` |$(tx)  |
               $(jl)| | |_| | | | (_| |$(tx)  |  Version $(VERSION)$(commit_date)
              $(jl)_/ |\\__'_|_|_|\\__'_|$(tx)  |  $(commit_string)
-            $(jl)|__/$(tx)                   |
+            $(jl)|__/$(tx)                   |  $(gc_version)
 
             """)
         end
     else
         if short
             print(io,"""
-              o  |  Version $(VERSION)$(commit_date)
+              o  |  Version $(VERSION)$(commit_date) $(gc_version)
              o o |  $(commit_string)
             """)
         else
@@ -1814,7 +1816,7 @@ function banner(io::IO = stdout; short = false)
               | | | | | | |/ _` |  |
               | | |_| | | | (_| |  |  Version $(VERSION)$(commit_date)
              _/ |\\__'_|_|_|\\__'_|  |  $(commit_string)
-            |__/                   |
+            |__/                   |  $(gc_version)
 
             """)
         end