don't save implicit imports into Main (JuliaLang#35415)

fix `eval` and `include` for userimg.jl

Author: JeffBezanson

base/sysimg.jl

@@ -82,24 +82,24 @@ empty!(LOAD_PATH)
 @eval Base creating_sysimg = false
 Base.init_load_path() # want to be able to find external packages in userimg.jl
 
-let
-tot_time_userimg = @elapsed (Base.isfile("userimg.jl") && Base.include(Main, "userimg.jl"))
+# Set up Main module
+import Base.MainInclude: eval, include
 
+Base.@eval Base let
+    ccall(:jl_clear_implicit_imports, Cvoid, (Any,), Main)
+    tot_time_userimg = @elapsed (isfile("userimg.jl") && include(Main, "userimg.jl"))
 
-tot_time_base = (Base.end_base_include - Base.start_base_include) * 10.0^(-9)
-tot_time = tot_time_base + Base.tot_time_stdlib[] + tot_time_userimg
+    tot_time_base = (end_base_include - start_base_include) * 10.0^(-9)
+    tot_time = tot_time_base + tot_time_stdlib[] + tot_time_userimg
 
-println("Sysimage built. Summary:")
-print("Total ─────── "); Base.time_print(tot_time               * 10^9); print(" \n");
-print("Base: ─────── "); Base.time_print(tot_time_base          * 10^9); print(" "); show(IOContext(stdout, :compact=>true), (tot_time_base          / tot_time) * 100); println("%")
-print("Stdlibs: ──── "); Base.time_print(Base.tot_time_stdlib[] * 10^9); print(" "); show(IOContext(stdout, :compact=>true), (Base.tot_time_stdlib[] / tot_time) * 100); println("%")
-if isfile("userimg.jl")
-print("Userimg: ──── "); Base.time_print(tot_time_userimg       * 10^9); print(" "); show(IOContext(stdout, :compact=>true), (tot_time_userimg       / tot_time) * 100); println("%")
-end
+    println("Sysimage built. Summary:")
+    print("Total ─────── "); time_print(tot_time               * 10^9); print(" \n");
+    print("Base: ─────── "); time_print(tot_time_base          * 10^9); print(" "); show(IOContext(stdout, :compact=>true), (tot_time_base          / tot_time) * 100); println("%")
+    print("Stdlibs: ──── "); time_print(tot_time_stdlib[] * 10^9); print(" "); show(IOContext(stdout, :compact=>true), (tot_time_stdlib[] / tot_time) * 100); println("%")
+    if isfile("userimg.jl")
+    print("Userimg: ──── "); time_print(tot_time_userimg       * 10^9); print(" "); show(IOContext(stdout, :compact=>true), (tot_time_userimg       / tot_time) * 100); println("%")
+    end
 end
 
-empty!(LOAD_PATH)
-empty!(DEPOT_PATH)
-
-# Set up Main module
-import Base.MainInclude: eval, include
+Base.empty!(LOAD_PATH)
+Base.empty!(DEPOT_PATH)

src/module.c

@@ -784,6 +784,25 @@ int jl_is_submodule(jl_module_t *child, jl_module_t *parent) JL_NOTSAFEPOINT
     }
 }
 
+// Remove implicitly imported identifiers, effectively resetting all the binding
+// resolution decisions for a module. This is dangerous, and should only be
+// done for modules that are essentially empty anyway. The only use case for this
+// is to leave `Main` as empty as possible in the default system image.
+JL_DLLEXPORT void jl_clear_implicit_imports(jl_module_t *m)
+{
+    size_t i;
+    JL_LOCK(&m->lock);
+    void **table = m->bindings.table;
+    for (i = 1; i < m->bindings.size; i+=2) {
+        if (table[i] != HT_NOTFOUND) {
+            jl_binding_t *b = (jl_binding_t*)table[i];
+            if (b->owner != m && !b->imported)
+                table[i] = HT_NOTFOUND;
+        }
+    }
+    JL_UNLOCK(&m->lock);
+}
+
 #ifdef __cplusplus
 }
 #endif