add --trim option for generating smaller binaries

Makefile

@@ -82,7 +82,7 @@ julia-deps: | $(DIRS) $(build_datarootdir)/julia/base $(build_datarootdir)/julia
 julia-stdlib: | $(DIRS) julia-deps
 	@$(MAKE) $(QUIET_MAKE) -C $(BUILDROOT)/stdlib
 
-julia-base: julia-deps $(build_sysconfdir)/julia/startup.jl $(build_man1dir)/julia.1 $(build_datarootdir)/julia/julia-config.jl
+julia-base: julia-deps $(build_sysconfdir)/julia/startup.jl $(build_man1dir)/julia.1 $(build_datarootdir)/julia/julia-config.jl $(build_datarootdir)/julia/juliac.jl $(build_datarootdir)/julia/juliac-buildscript.jl
 	@$(MAKE) $(QUIET_MAKE) -C $(BUILDROOT)/base
 
 julia-libccalltest: julia-deps
@@ -181,7 +181,7 @@ $(build_sysconfdir)/julia/startup.jl: $(JULIAHOME)/etc/startup.jl | $(build_sysc
 	@echo Creating usr/etc/julia/startup.jl
 	@cp $< $@
 
-$(build_datarootdir)/julia/julia-config.jl: $(JULIAHOME)/contrib/julia-config.jl | $(build_datarootdir)/julia
+$(build_datarootdir)/julia/%: $(JULIAHOME)/contrib/% | $(build_datarootdir)/julia
 	$(INSTALL_M) $< $(dir $@)
 
 $(build_depsbindir)/stringreplace: $(JULIAHOME)/contrib/stringreplace.c | $(build_depsbindir)

NEWS.md

@@ -4,6 +4,8 @@ Julia v1.12 Release Notes
 New language features
 ---------------------
 
+- New option `--trim` for building "trimmed" binaries, where code not provably reachable from entry points
+  is removed. Entry points can be marked using `Base.Experimental.entrypoint` ([#55047]).
 - A new keyword argument `usings::Bool` has been added to `names`. By using this, we can now
   find all the names available in module `A` by `names(A; all=true, imported=true, usings=true)`. ([#54609])
 - the `@atomic(...)` macro family supports now the reference assignment syntax, e.g.

base/experimental.jl

@@ -457,4 +457,18 @@ without adding them to the global method table.
 """
 :@MethodTable
 
+"""
+    Base.Experimental.entrypoint(f, argtypes::Tuple)
+
+Mark a method for inclusion when the `--trim` option is specified.
+"""
+function entrypoint(@nospecialize(f), @nospecialize(argtypes::Tuple))
+    entrypoint(Tuple{Core.Typeof(f), argtypes...})
+end
+
+function entrypoint(@nospecialize(argt::Type))
+    ccall(:jl_add_entrypoint, Int32, (Any,), argt)
+    nothing
+end
+
 end

base/libuv.jl

@@ -133,7 +133,10 @@ function uv_return_spawn end
 function uv_asynccb end
 function uv_timercb end
 
-function reinit_stdio()
+reinit_stdio() = _reinit_stdio()
+# we need this so it can be called by codegen to print errors, even after
+# reinit_stdio has been redefined by the juliac build script.
+function _reinit_stdio()
     global stdin = init_stdio(ccall(:jl_stdin_stream, Ptr{Cvoid}, ()))::IO
     global stdout = init_stdio(ccall(:jl_stdout_stream, Ptr{Cvoid}, ()))::IO
     global stderr = init_stdio(ccall(:jl_stderr_stream, Ptr{Cvoid}, ()))::IO

base/options.jl

@@ -58,6 +58,7 @@ struct JLOptions
     permalloc_pkgimg::Int8
     heap_size_hint::UInt64
     trace_compile_timing::Int8
+    trim::Int8
 end
 
 # This runs early in the sysimage != is not defined yet

base/reflection.jl

@@ -1504,6 +1504,13 @@ struct CodegenParams
     """
     use_jlplt::Cint
 
+    """
+    If enabled, only provably reachable code (from functions marked with `entrypoint`) is included
+    in the output system image. Errors or warnings can be given for call sites too dynamic to handle.
+    The option is disabled by default. (0=>disabled, 1=>safe (static errors), 2=>unsafe, 3=>unsafe plus warnings)
+    """
+    trim::Cint
+
     """
     A pointer of type
 
@@ -1519,14 +1526,14 @@ struct CodegenParams
                    prefer_specsig::Bool=false,
                    gnu_pubnames::Bool=true, debug_info_kind::Cint = default_debug_info_kind(),
                    debug_info_level::Cint = Cint(JLOptions().debug_level), safepoint_on_entry::Bool=true,
-                   gcstack_arg::Bool=true, use_jlplt::Bool=true,
+                   gcstack_arg::Bool=true, use_jlplt::Bool=true, trim::Cint=Cint(0),
                    lookup::Ptr{Cvoid}=unsafe_load(cglobal(:jl_rettype_inferred_addr, Ptr{Cvoid})))
         return new(
             Cint(track_allocations), Cint(code_coverage),
             Cint(prefer_specsig),
             Cint(gnu_pubnames), debug_info_kind,
             debug_info_level, Cint(safepoint_on_entry),
-            Cint(gcstack_arg), Cint(use_jlplt),
+            Cint(gcstack_arg), Cint(use_jlplt), Cint(trim),
             lookup)
     end
 end

base/strings/io.jl

@@ -51,6 +51,8 @@ function print(io::IO, xs...)
     return nothing
 end
 
+setfield!(typeof(print).name.mt, :max_args, 10, :monotonic)
+
 """
     println([io::IO], xs...)
 
@@ -74,6 +76,7 @@ julia> String(take!(io))
 """
 println(io::IO, xs...) = print(io, xs..., "\n")
 
+setfield!(typeof(println).name.mt, :max_args, 10, :monotonic)
 ## conversion of general objects to strings ##
 
 """
@@ -149,6 +152,7 @@ function print_to_string(xs...)
     end
     String(_unsafe_take!(s))
 end
+setfield!(typeof(print_to_string).name.mt, :max_args, 10, :monotonic)
 
 function string_with_env(env, xs...)
     if isempty(xs)

contrib/julia-config.jl

@@ -67,7 +67,7 @@ function ldlibs(doframework)
         "julia"
     end
     if Sys.isunix()
-        return "-Wl,-rpath,$(shell_escape(libDir())) -Wl,-rpath,$(shell_escape(private_libDir())) -l$libname"
+        return "-L$(shell_escape(private_libDir())) -Wl,-rpath,$(shell_escape(libDir())) -Wl,-rpath,$(shell_escape(private_libDir())) -l$libname"
     else
         return "-l$libname -lopenlibm"
     end