Libdl: better support for musl

We previously claimed that:
"Skip over objects without a path (as they represent this own object)"
This was false on two levels:
 - On everything non-glibc the binary does have a path
 - On linux, there is also usually also at least one shim object that does not have a path

So instead, we filter these out explicitly at the end (and remove some duplicate code paths).

stdlib/Libdl/src/Libdl.jl

@@ -209,7 +209,7 @@ File extension for dynamic libraries (e.g. dll, dylib, so) on the current platfo
 """
 dlext
 
-if Sys.islinux()
+if (Sys.islinux() || Sys.isbsd()) && !Sys.isapple()
  struct dl_phdr_info
  # Base address of object
  addr::Cuint
@@ -224,51 +224,18 @@ if Sys.islinux()
  phnum::Cshort
  end
 
- # This callback function called by dl_iterate_phdr() on Linux
- function dl_phdr_info_callback(di::dl_phdr_info, size::Csize_t, dynamic_libraries::Array{String,1})
- # Skip over objects without a path (as they represent this own object)
- name = unsafe_string(di.name)
- if !isempty(name)
- push!(dynamic_libraries, name)
- end
- return convert(Cint, 0)::Cint
- end
-end # linux-only
-
-if Sys.isbsd() && !Sys.isapple()
+ # This callback function called by dl_iterate_phdr() on Linux and BSD's
  # DL_ITERATE_PHDR(3) on freebsd
- struct dl_phdr_info
- # Base address of object
- addr::Cuint
-
- # Null-terminated name of object
- name::Ptr{UInt8}
-
- # Pointer to array of ELF program headers for this object
- phdr::Ptr{Cvoid}
-
- # Number of program headers for this object
- phnum::Cshort
- end
-
- function dl_phdr_info_callback(di::dl_phdr_info, size::Csize_t, dy_libs::Vector{String})
+ function dl_phdr_info_callback(di::dl_phdr_info, size::Csize_t, dynamic_libraries::Array{String,1})
  name = unsafe_string(di.name)
- if !isempty(name)
- push!(dy_libs, name)
- end
- return convert(Cint, 0)::Cint
+ push!(dynamic_libraries, name)
+ return Cint(0)
  end
-end # bsd family
+end
 
 function dllist()
  dynamic_libraries = Vector{String}()
 
- @static if Sys.islinux()
- callback = @cfunction(dl_phdr_info_callback, Cint,
- (Ref{dl_phdr_info}, Csize_t, Ref{Vector{String}}))
- ccall(:dl_iterate_phdr, Cint, (Ptr{Cvoid}, Ref{Vector{String}}), callback, dynamic_libraries)
- end
-
  @static if Sys.isapple()
  numImages = ccall(:_dyld_image_count, Cint, ())
 
@@ -277,17 +244,16 @@ function dllist()
  name = unsafe_string(ccall(:_dyld_get_image_name, Cstring, (UInt32,), i))
  push!(dynamic_libraries, name)
  end
- end
-
- @static if Sys.iswindows()
- ccall(:jl_dllist, Cint, (Any,), dynamic_libraries)
- end
-
- @static if Sys.isbsd() && !Sys.isapple()
+ elseif Sys.islinux() || Sys.isbsd()
  callback = @cfunction(dl_phdr_info_callback, Cint,
  (Ref{dl_phdr_info}, Csize_t, Ref{Vector{String}}))
  ccall(:dl_iterate_phdr, Cint, (Ptr{Cvoid}, Ref{Vector{String}}), callback, dynamic_libraries)
  popfirst!(dynamic_libraries)
+ filter!(!isempty, dynamic_libraries)
+ elseif Sys.iswindows()
+ ccall(:jl_dllist, Cint, (Any,), dynamic_libraries)
+ else
+ # unimplemented
  end
 
  return dynamic_libraries