Infrastructure for hiding backtrace frames

This implements a hide_in_backtrace meta which may be attached to
individual methods (via a flag on the CodeInfo) to mark them for hiding
in backtraces.

Use this infrastructure to hide several julia methods by default (these
can still be seen using the internal_funcs flag to backtrace())
* error(), backtrace(), stacktrace()
* keyword sorters

Author: c42f

base/error.jl

@@ -30,7 +30,11 @@ throw
 
 Raise an `ErrorException` with the given message.
 """
-error(s::AbstractString) = throw(ErrorException(s))
+function error(s::AbstractString)
+    @_noinline_meta
+    @_hide_in_stacktrace_meta
+    throw(ErrorException(s))
+end
 
 """
     error(msg...)
@@ -39,6 +43,7 @@ Raise an `ErrorException` with the given message.
 """
 function error(s::Vararg{Any,N}) where {N}
     @_noinline_meta
+    @_hide_in_stacktrace_meta
     throw(ErrorException(Main.Base.string(s...)))
 end
 
@@ -106,8 +111,10 @@ Get a backtrace object for the current program point.
 """
 function backtrace()
     @_noinline_meta
-    # skip frame for backtrace(). Note that for this to work properly,
-    # backtrace() itself must not be interpreted nor inlined.
+    @_hide_in_stacktrace_meta
+    # skip frame for backtrace(). Note that with `skip > 0` backtrace() must
+    # not be inlined to avoid loosing parent frames.
+    # We also tag it as hidden in case it gets interpreted.
     skip = 1
     bt1, bt2 = ccall(:jl_backtrace_from_here, Ref{SimpleVector}, (Cint, Cint), false, skip)
     return _reformat_bt(bt1::Vector{Ptr{Cvoid}}, bt2::Vector{Any})

base/errorshow.jl

@@ -745,11 +745,6 @@ function show_backtrace(io::IO, t::Vector{Any})
     end
 end
 
-function is_kw_sorter_name(name::Symbol)
-    sn = string(name)
-    return !startswith(sn, '#') && endswith(sn, "##kw")
-end
-
 function process_backtrace(t::Vector, limit::Int=typemax(Int); skipC = true)
     n = 0
     last_frame = StackTraces.UNKNOWN
@@ -762,25 +757,26 @@ function process_backtrace(t::Vector, limit::Int=typemax(Int); skipC = true)
         else
             lkups = StackTraces.lookup(lkups)
         end
-        for lkup in lkups
-            if lkup === StackTraces.UNKNOWN
+        for frame in lkups
+            if frame === StackTraces.UNKNOWN
                 continue
             end
 
-            if (lkup.from_c && skipC) || is_kw_sorter_name(lkup.func)
+            if StackTraces.is_hidden(frame) && skipC
                 continue
             end
             count += 1
             if count > limit
                 break
             end
 
-            if lkup.file != last_frame.file || lkup.line != last_frame.line || lkup.func != last_frame.func || lkup.linfo !== lkup.linfo
+            if frame.file != last_frame.file || frame.line != last_frame.line ||
+                    frame.func != last_frame.func || frame.linfo !== last_frame.linfo
                 if n > 0
                     push!(ret, (last_frame, n))
                 end
                 n = 1
-                last_frame = lkup
+                last_frame = frame
             else
                 n += 1
             end

base/essentials.jl

@@ -113,6 +113,9 @@ end
 macro _propagate_inbounds_meta()
     return Expr(:meta, :inline, :propagate_inbounds)
 end
+macro _hide_in_stacktrace_meta()
+    return Expr(:meta, :hide_in_stacktrace)
+end
 
 function iterate end
 

base/expr.jl

@@ -237,6 +237,18 @@ macro pure(ex)
     esc(isa(ex, Expr) ? pushmeta!(ex, :pure) : ex)
 end
 
+"""
+    @hide_in_stacktrace
+
+Mark a function to be hidden from the user in stacktraces. `@hide_in_stacktrace`
+currently implies `@noinline`, though this may be relaxed in the future.
+
+See also [`stacktrace`](@ref).
+"""
+macro hide_in_stacktrace(ex)
+    esc(ex isa Expr ? pushmeta!(pushmeta!(ex, :hide_in_stacktrace), :noinline) : ex)
+end
+
 """
     @propagate_inbounds
 

base/stacktraces.jl

@@ -95,6 +95,20 @@ function hash(frame::StackFrame, h::UInt)
     return h
 end
 
+# Determine whether frame should be hidden from the user by default
+function is_hidden(frame::StackFrame)
+    if frame.from_c
+        return true
+    end
+    if frame.linfo isa Core.MethodInstance
+        # NB: MethodInstance currently only available for non-inlined frames.
+        def = frame.linfo.def
+        if def isa Method
+            return ccall(:jl_ir_flag_hide_in_stacktrace, Bool, (Any,), def.source)
+        end
+    end
+    return false
+end
 
 """
     lookup(pointer::Ptr{Cvoid}) -> Vector{StackFrame}
@@ -151,32 +165,30 @@ function lookup(ip::Base.InterpreterIP)
 end
 
 """
-    stacktrace([trace::Vector{Ptr{Cvoid}},] [c_funcs::Bool=false]) -> StackTrace
+    stacktrace([rawtrace,] internal_funcs=false)
+
+Returns a stack trace in the form of a vector of `StackFrame`s from the current
+call stack, or from a raw call stack `rawtrace` which must have been previously
+collected using `backtrace()`.
 
-Returns a stack trace in the form of a vector of `StackFrame`s. (By default stacktrace
-doesn't return C functions, but this can be enabled.) When called without specifying a
-trace, `stacktrace` first calls `backtrace`.
+By default `stacktrace` filters out internal functions, including C functions
+and any Julia functions marked with `Base.@hide_in_stacktrace`. These can be
+included by setting `internal_funcs` to `true`.
 """
-function stacktrace(trace::Vector{<:Union{Base.InterpreterIP,Ptr{Cvoid}}}, c_funcs::Bool=false)
+function stacktrace(rawtrace::AbstractVector, internal_funcs::Bool=false)
     stack = StackTrace()
-    for ip in trace
+    for ip in rawtrace
         for frame in lookup(ip)
-            # Skip frames that come from C calls.
-            if c_funcs || !frame.from_c
+            if internal_funcs || !is_hidden(frame)
                 push!(stack, frame)
             end
         end
     end
     return stack
 end
 
-function stacktrace(c_funcs::Bool=false)
-    stack = stacktrace(backtrace(), c_funcs)
-    # Remove frame for this function (and any functions called by this function).
-    remove_frames!(stack, :stacktrace)
-    # also remove all of the non-Julia functions that led up to this point (if that list is non-empty)
-    c_funcs && deleteat!(stack, 1:(something(findfirst(frame -> !frame.from_c, stack), 1) - 1))
-    return stack
+@noinline Base.@hide_in_stacktrace function stacktrace(internal_funcs::Bool=false)
+    stacktrace(backtrace(), internal_funcs)
 end
 
 """

src/ast.c

@@ -62,6 +62,7 @@ jl_sym_t *throw_undef_if_not_sym; jl_sym_t *getfield_undefref_sym;
 jl_sym_t *gc_preserve_begin_sym; jl_sym_t *gc_preserve_end_sym;
 jl_sym_t *coverageeffect_sym; jl_sym_t *escape_sym;
 jl_sym_t *aliasscope_sym; jl_sym_t *popaliasscope_sym;
+jl_sym_t *hide_in_stacktrace_sym;
 
 static uint8_t flisp_system_image[] = {
 #include <julia_flisp.boot.inc>
@@ -368,6 +369,7 @@ void jl_init_frontend(void)
     copyast_sym = jl_symbol("copyast");
     loopinfo_sym = jl_symbol("loopinfo");
     pure_sym = jl_symbol("pure");
+    hide_in_stacktrace_sym = jl_symbol("hide_in_stacktrace");
     meta_sym = jl_symbol("meta");
     list_sym = jl_symbol("list");
     unused_sym = jl_symbol("#unused#");

src/dump.c

@@ -2565,7 +2565,8 @@ JL_DLLEXPORT jl_array_t *jl_compress_ir(jl_method_t *m, jl_code_info_t *code)
         NULL
     };
 
-    uint8_t flags = (code->inferred << 3)
+    uint8_t flags = (code->hide_in_stacktrace << 4)
+                  | (code->inferred << 3)
                   | (code->inlineable << 2)
                   | (code->propagate_inbounds << 1)
                   | (code->pure << 0);
@@ -2651,6 +2652,7 @@ JL_DLLEXPORT jl_code_info_t *jl_uncompress_ir(jl_method_t *m, jl_code_instance_t
 
     jl_code_info_t *code = jl_new_code_info_uninit();
     uint8_t flags = read_uint8(s.s);
+    code->hide_in_stacktrace = !!(flags & (1 << 4));
     code->inferred = !!(flags & (1 << 3));
     code->inlineable = !!(flags & (1 << 2));
     code->propagate_inbounds = !!(flags & (1 << 1));
@@ -2704,6 +2706,15 @@ JL_DLLEXPORT jl_code_info_t *jl_uncompress_ir(jl_method_t *m, jl_code_instance_t
     return code;
 }
 
+JL_DLLEXPORT uint8_t jl_ir_flag_hide_in_stacktrace(jl_array_t *data)
+{
+    if (jl_is_code_info(data))
+        return ((jl_code_info_t*)data)->hide_in_stacktrace;
+    assert(jl_typeis(data, jl_array_uint8_type));
+    uint8_t flags = ((uint8_t*)data->data)[0];
+    return !!(flags & (1 << 4));
+}
+
 JL_DLLEXPORT uint8_t jl_ir_flag_inferred(jl_array_t *data)
 {
     if (jl_is_code_info(data))

src/jltypes.c

@@ -2080,7 +2080,7 @@ void jl_init_types(void) JL_GC_DISABLED
     jl_code_info_type =
         jl_new_datatype(jl_symbol("CodeInfo"), core,
                         jl_any_type, jl_emptysvec,
-                        jl_perm_symsvec(18,
+                        jl_perm_symsvec(19,
                             "code",
                             "codelocs",
                             "ssavaluetypes",
@@ -2095,11 +2095,12 @@ void jl_init_types(void) JL_GC_DISABLED
                             "edges",
                             "min_world",
                             "max_world",
+                            "hide_in_stacktrace",
                             "inferred",
                             "inlineable",
                             "propagate_inbounds",
                             "pure"),
-                        jl_svec(18,
+                        jl_svec(19,
                             jl_array_any_type,
                             jl_any_type,
                             jl_any_type,
@@ -2117,8 +2118,9 @@ void jl_init_types(void) JL_GC_DISABLED
                             jl_bool_type,
                             jl_bool_type,
                             jl_bool_type,
+                            jl_bool_type,
                             jl_bool_type),
-                        0, 1, 18);
+                        0, 1, 19);
 
     jl_method_type =
         jl_new_datatype(jl_symbol("Method"), core,

src/julia-syntax.scm

@@ -499,6 +499,7 @@
           name positional-sparams pargl-all
           `(block
             ,@(without-generated prologue)
+            (meta hide_in_stacktrace)
             ,(let (;; call mangled(vals..., [rest_kw,] pargs..., [vararg]...)
                    (ret `(return (call ,mangled
                                        ,@(if ordered-defaults keynames vals)
@@ -519,6 +520,7 @@
              (call (core kwftype) ,ftype)) ,kw ,@pargl ,@vararg)
           `(block
             ,@(filter linenum? prologue)
+            (meta hide_in_stacktrace)
             ,(scopenest
               keynames
               (map (lambda (v dflt)

src/julia.h

@@ -264,6 +264,7 @@ typedef struct _jl_code_info_t {
     size_t min_world;
     size_t max_world;
     // various boolean properties:
+    uint8_t hide_in_stacktrace;
     uint8_t inferred;
     uint8_t inlineable;
     uint8_t propagate_inbounds;
@@ -1651,6 +1652,7 @@ JL_DLLEXPORT jl_value_t *jl_copy_ast(jl_value_t *expr JL_MAYBE_UNROOTED);
 // IR representation
 JL_DLLEXPORT jl_array_t *jl_compress_ir(jl_method_t *m, jl_code_info_t *code);
 JL_DLLEXPORT jl_code_info_t *jl_uncompress_ir(jl_method_t *m, jl_code_instance_t *metadata, jl_array_t *data);
+JL_DLLEXPORT uint8_t jl_ir_flag_hide_in_stacktrace(jl_array_t *data) JL_NOTSAFEPOINT;
 JL_DLLEXPORT uint8_t jl_ir_flag_inferred(jl_array_t *data) JL_NOTSAFEPOINT;
 JL_DLLEXPORT uint8_t jl_ir_flag_inlineable(jl_array_t *data) JL_NOTSAFEPOINT;
 JL_DLLEXPORT uint8_t jl_ir_flag_pure(jl_array_t *data) JL_NOTSAFEPOINT;