add --strip-metadata option

NEWS.md

@@ -37,6 +37,8 @@ Compiler/Runtime improvements
 Command-line option changes
 ---------------------------
 
+* New option `--strip-metadata` to remove docstrings, source location information, and local
+  variable names when building a system image.
 
 Multi-threading changes
 -----------------------

base/docs/Docs.jl

@@ -74,15 +74,15 @@ const META    = gensym(:meta)
 const METAType = IdDict{Any,Any}
 
 function meta(m::Module)
-    if !isdefined(m, META)
+    if !isdefined(m, META) || getfield(m, META) === nothing
         initmeta(m)
     end
     return getfield(m, META)::METAType
 end
 
 function initmeta(m::Module)
-    if !isdefined(m, META)
-        Core.eval(m, :(const $META = $(METAType())))
+    if !isdefined(m, META) || getfield(m, META) === nothing
+        Core.eval(m, :($META = $(METAType())))
         push!(modules, m)
     end
     nothing

base/loading.jl

@@ -765,7 +765,7 @@ function _include_from_serialized(path::String, depmods::Vector{Any})
     restored = sv[1]::Vector{Any}
     for M in restored
         M = M::Module
-        if isdefined(M, Base.Docs.META)
+        if isdefined(M, Base.Docs.META) && getfield(M, Base.Docs.META) !== nothing
             push!(Base.Docs.modules, M)
         end
         if parentmodule(M) === M

base/options.jl

@@ -47,6 +47,7 @@ struct JLOptions
     warn_scope::Int8
     image_codegen::Int8
     rr_detach::Int8
+    strip_metadata::Int8
 end
 
 # This runs early in the sysimage != is not defined yet

src/codegen.cpp

@@ -7038,7 +7038,7 @@ static std::pair<std::unique_ptr<Module>, jl_llvm_functions_t>
     };
     std::vector<unsigned> current_lineinfo, new_lineinfo;
     auto coverageVisitStmt = [&] (size_t dbg) {
-        if (dbg == 0)
+        if (dbg == 0 || dbg >= linetable.size())
             return;
         // Compute inlining stack for current line, inner frame first
         while (dbg) {
@@ -7131,8 +7131,10 @@ static std::pair<std::unique_ptr<Module>, jl_llvm_functions_t>
         sync_bytes = ctx.builder.CreateCall(prepare_call(diff_gc_total_bytes_func), {});
     { // coverage for the function definition line number
         const auto &topinfo = linetable.at(0);
-        if (topinfo == linetable.at(1))
-            current_lineinfo.push_back(1);
+        if (linetable.size() > 1) {
+            if (topinfo == linetable.at(1))
+                current_lineinfo.push_back(1);
+        }
         if (do_coverage(topinfo.is_user_code))
             coverageVisitLine(ctx, topinfo.file, topinfo.line);
     }

src/jloptions.c

@@ -79,6 +79,7 @@ JL_DLLEXPORT void jl_init_options(void)
                         JL_OPTIONS_WARN_SCOPE_ON,  // ambiguous scope warning
                         0, // image-codegen
                         0, // rr-detach
+                        0, // strip-metadata
     };
     jl_options_initialized = 1;
 }
@@ -163,6 +164,7 @@ static const char opts_hidden[]  =
     // compiler output options
     " --output-o name           Generate an object file (including system image data)\n"
     " --output-ji name          Generate a system image data file (.ji)\n"
+    " --strip-metadata          Remove docstrings and source location info from system image\n"
 
     // compiler debugging (see the devdocs for tips on using these options)
     " --output-unopt-bc name    Generate unoptimized LLVM bitcode (.bc)\n"
@@ -212,6 +214,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
            opt_bug_report,
            opt_image_codegen,
            opt_rr_detach,
+           opt_strip_metadata,
     };
     static const char* const shortopts = "+vhqH:e:E:L:J:C:it:p:O:g:";
     static const struct option longopts[] = {
@@ -265,6 +268,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
         { "lisp",            no_argument,       0, 1 },
         { "image-codegen",   no_argument,       0, opt_image_codegen },
         { "rr-detach",       no_argument,       0, opt_rr_detach },
+        { "strip-metadata",  no_argument,       0, opt_strip_metadata },
         { 0, 0, 0, 0 }
     };
 
@@ -689,6 +693,9 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
         case opt_rr_detach:
             jl_options.rr_detach = 1;
             break;
+        case opt_strip_metadata:
+            jl_options.strip_metadata = 1;
+            break;
         default:
             jl_errorf("julia: unhandled option -- %c\n"
                       "This is a bug, please report it.", c);

src/jloptions.h

@@ -51,6 +51,7 @@ typedef struct {
     int8_t warn_scope;
     int8_t image_codegen;
     int8_t rr_detach;
+    int8_t strip_metadata;
 } jl_options_t;
 
 #endif

src/staticdata.c

@@ -266,6 +266,8 @@ static jl_typename_t *jl_idtable_typename = NULL;
 static jl_value_t *jl_bigint_type = NULL;
 static int gmp_limb_size = 0;
 
+static jl_sym_t *jl_docmeta_sym = NULL;
+
 enum RefTags {
     DataRef,
     ConstDataRef,
@@ -399,7 +401,10 @@ static void jl_serialize_module(jl_serializer_state *s, jl_module_t *m)
             jl_serialize_value(s, (jl_value_t*)table[i]);
             jl_binding_t *b = (jl_binding_t*)table[i+1];
             jl_serialize_value(s, b->name);
-            jl_serialize_value(s, jl_atomic_load_relaxed(&b->value));
+            if (jl_docmeta_sym && b->name == jl_docmeta_sym && jl_options.strip_metadata)
+                jl_serialize_value(s, jl_nothing);
+            else
+                jl_serialize_value(s, jl_atomic_load_relaxed(&b->value));
             jl_serialize_value(s, jl_atomic_load_relaxed(&b->globalref));
             jl_serialize_value(s, b->owner);
         }
@@ -651,7 +656,10 @@ static void jl_write_module(jl_serializer_state *s, uintptr_t item, jl_module_t
             record_gvar(s, jl_get_llvm_gv(native_functions, (jl_value_t*)b),
                     ((uintptr_t)DataRef << RELOC_TAG_OFFSET) + binding_reloc_offset);
             write_pointerfield(s, (jl_value_t*)b->name);
-            write_pointerfield(s, jl_atomic_load_relaxed(&b->value));
+            if (jl_docmeta_sym && b->name == jl_docmeta_sym && jl_options.strip_metadata)
+                write_pointerfield(s, jl_nothing);
+            else
+                write_pointerfield(s, jl_atomic_load_relaxed(&b->value));
             write_pointerfield(s, jl_atomic_load_relaxed(&b->globalref));
             write_pointerfield(s, (jl_value_t*)b->owner);
             size_t flag_offset = offsetof(jl_binding_t, owner) + sizeof(b->owner);
@@ -1519,6 +1527,81 @@ static void jl_prune_type_cache_linear(jl_svec_t *cache)
     }
 }
 
+static jl_value_t *strip_codeinfo(jl_method_t *m, jl_value_t *ci_, int isdef)
+{
+    jl_code_info_t *ci = NULL;
+    JL_GC_PUSH1(&ci);
+    int compressed = 0;
+    if (!jl_is_code_info(ci_)) {
+        compressed = 1;
+        ci = jl_uncompress_ir(m, NULL, (jl_array_t*)ci_);
+    }
+    else {
+        ci = (jl_code_info_t*)ci_;
+    }
+    // leave codelocs length the same so the compiler can assume that; just zero it
+    memset(jl_array_data(ci->codelocs), 0, jl_array_len(ci->codelocs)*sizeof(int32_t));
+    // empty linetable
+    if (jl_is_array(ci->linetable))
+        jl_array_del_end((jl_array_t*)ci->linetable, jl_array_len(ci->linetable));
+    // replace slot names with `?`, except unused_sym since the compiler looks at it
+    jl_sym_t *questionsym = jl_symbol("?");
+    int i, l = jl_array_len(ci->slotnames);
+    for (i = 0; i < l; i++) {
+        jl_value_t *s = jl_array_ptr_ref(ci->slotnames, i);
+        if (s != (jl_value_t*)jl_unused_sym)
+            jl_array_ptr_set(ci->slotnames, i, questionsym);
+    }
+    if (isdef) {
+        m->slot_syms = jl_compress_argnames(ci->slotnames);
+        jl_gc_wb(m, m->slot_syms);
+    }
+    jl_value_t *ret = (jl_value_t*)ci;
+    if (compressed)
+        ret = (jl_value_t*)jl_compress_ir(m, ci);
+    JL_GC_POP();
+    return ret;
+}
+
+static void strip_specializations_(jl_method_instance_t *mi)
+{
+    assert(jl_is_method_instance(mi));
+    jl_code_instance_t *codeinst = mi->cache;
+    while (codeinst) {
+        if (codeinst->inferred && codeinst->inferred != jl_nothing) {
+            codeinst->inferred = strip_codeinfo(mi->def.method, codeinst->inferred, 0);
+            jl_gc_wb(codeinst, codeinst->inferred);
+        }
+        codeinst = jl_atomic_load_relaxed(&codeinst->next);
+    }
+}
+
+static int strip_all_codeinfos__(jl_typemap_entry_t *def, void *_env)
+{
+    jl_method_t *m = def->func.method;
+    if (m->source) {
+        m->source = strip_codeinfo(m, m->source, 1);
+        jl_gc_wb(m, m->source);
+    }
+    jl_svec_t *specializations = def->func.method->specializations;
+    size_t i, l = jl_svec_len(specializations);
+    for (i = 0; i < l; i++) {
+        jl_value_t *mi = jl_svecref(specializations, i);
+        if (mi != jl_nothing)
+            strip_specializations_((jl_method_instance_t*)mi);
+    }
+    return 1;
+}
+
+static void strip_all_codeinfos_(jl_methtable_t *mt, void *_env)
+{
+    jl_typemap_visitor(mt->defs, strip_all_codeinfos__, NULL);
+}
+
+static void jl_strip_all_codeinfos(void)
+{
+    jl_foreach_reachable_mtable(strip_all_codeinfos_, NULL);
+}
 
 // --- entry points ---
 
@@ -1527,6 +1610,8 @@ static void jl_cleanup_serializer2(void);
 
 static void jl_save_system_image_to_stream(ios_t *f) JL_GC_DISABLED
 {
+    if (jl_options.strip_metadata)
+        jl_strip_all_codeinfos();
     jl_gc_collect(JL_GC_FULL);
     jl_gc_collect(JL_GC_INCREMENTAL);   // sweep finalizers
     JL_TIMING(SYSIMG_DUMP);
@@ -1570,6 +1655,12 @@ static void jl_save_system_image_to_stream(ios_t *f) JL_GC_DISABLED
         gmp_limb_size = jl_unbox_long(jl_get_global((jl_module_t*)jl_get_global(jl_base_module, jl_symbol("GMP")),
                                                     jl_symbol("BITS_PER_LIMB"))) / 8;
     }
+    if (jl_base_module) {
+        jl_value_t *docs = jl_get_global(jl_base_module, jl_symbol("Docs"));
+        if (docs && jl_is_module(docs)) {
+            jl_docmeta_sym = (jl_sym_t*)jl_get_global((jl_module_t*)docs, jl_symbol("META"));
+        }
+    }
 
     { // step 1: record values (recursively) that need to go in the image
         size_t i;