Fix link problem with Xcode 15

[bjorng]

The dynamic libraries for the wx application would fail to build with the new linker in Xcode 15 for macOS. One workaround is to force the old linker to be used, but that will stop working when the the old linker is eventually retired.

It turns out that wx uses a very old way to create dynamic libraries. Essentially it asks the linker to accept that there are references to undefined symbols, trusting that they will be defined when the dynamic library is loaded. That is done using the following options:

-bundle -flat_namespace -undefined suppress

The option -undefined suppress is deprecated by the new linker and it will consider undefined symbols to be an error.

A more modern approaph to creating dynamic libraries is to use the the -bundle_loader option to point out an executable that can be used to satisfy references to undefined symbols:

 -bundle -bundle_loader $ERL_TOP/bin/aarch64-apple-darwin22.6.0/beam.smp

Care must be taken not to include the -bundler_loader option in configure tests that test linking, because the beam.smp executable has not been built at that time and the linker in older Xcode releases will complain if the executable does not exist. It seems that Xcode 15 will check that the executable exists only if there are references to undefined symbols.

While at it, update the ancient build instructions for wxWidgets.

[github-actions]

CT Test Results

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// Erlang/OTP Github Action Bot

[jj1bdx]

@bjorng

Summary

One more fix is needed for Xcode 15 to link the wx driver, to suppress undefined error messages during the configuration testing phase, by adding -undefined suppress to the linker flag.

My running environment

Mac mini 2013 M2 Pro, macOS 13.5.2, Xcode Command Line Tools 15.0, wxwidgets 3.2.2.1 from Homebrew

Synopsis

I've applied the patch in this PR to OTP-26.1, but this patch alone didn't solve the following error during running configure:

checking if we can link wxwidgets programs... no

This error prevents building wxe_driver although this error only generates following warning during configure:

configure: WARNING: Can not link wx program are all developer packages installed?

So this error does not stop the build but wxe_driver.so was not built.

The error is generated during executing the following test program:

otp/lib/wx/configure

Lines 7017 to 7082 in e3dfb18

	{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if we can link wxwidgets programs" >&5
	printf %s "checking if we can link wxwidgets programs... " >&6; }
	saved_LIBS=$LIBS
	if test X"$WX_HAVE_STATIC_LIBS" = X"true" ; then
	LIBS=$WX_LIBS_STATIC
	fi
	cat confdefs.h - <<_ACEOF >conftest.$ac_ext
	/* end confdefs.h. */
	#include "wx/wx.h"
	#include "wx/stc/stc.h"
	class MyApp : public wxApp
	{
	virtual bool OnInit() {
	// Test that we have a FromUTF8
	// it isn't in too old wxWidgets versions
	wxString test = wxString::FromUTF8((const char *)"foo");
	wxStyledTextCtrl * foo = new wxStyledTextCtrl();
	return foo;
	};
	};
	IMPLEMENT_APP(MyApp)
	_ACEOF
	if ac_fn_cxx_try_link "$LINENO"
	then :
	CAN_LINK_WX=yes
	else $as_nop
	CAN_LINK_WX=no
	fi
	rm -f core conftest.err conftest.$ac_objext conftest.beam \
	conftest$ac_exeext conftest.$ac_ext
	CXXFLAGS=$saved_CXXFLAGS
	LIBS=$saved_LIBS
	ac_ext=c
	ac_cpp='$CPP $CPPFLAGS'
	ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
	ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
	ac_compiler_gnu=$ac_cv_c_compiler_gnu
	{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $CAN_LINK_WX" >&5
	printf "%s\n" "$CAN_LINK_WX" >&6; }
	if test X"$CAN_LINK_WX" != X"yes" ; then
	echo "Can not link wx program are all developer packages installed?" >> ./CONF_INFO
	WXERL_CAN_BUILD_DRIVER=false
	if test X"$with_wx" = X"yes" ; then
	as_fn_error $? "Can not link wx program are all developer packages installed?" "$LINENO" 5
	else
	{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: Can not link wx program are all developer packages installed?" >&5
	printf "%s\n" "$as_me: WARNING: Can not link wx program are all developer packages installed?" >&2;}
	fi
	fi
	fi

I've attached a related part of configure error log in lib/wx:

configure-error-log.txt

The error shows a massive number of undefined symbol errors as in the following excerpt:

configure:7046: g++ -o conftest  -g -Wall -fPIC -g -O2 -mmacosx-version-min=13 -Wno-deprecate
d-declarations -fno-strict-aliasing  -D_MACOSX -D_THREAD_SAFE -D_REENTRANT -I/opt/homebrew/li
b/wx/include/osx_cocoa-unicode-3.2 -I/opt/homebrew/include/wx-3.2 -D_FILE_OFFSET_BITS=64 -DWX
USINGDLL -D__WXMAC__ -D__WXOSX__ -D__WXOSX_COCOA__   -D_MACOSX -D_THREAD_SAFE -D_REENTRANT -m
macosx-version-min=13 -bundle -fPIC  conftest.cpp  >&5
In file included from conftest.cpp:31:
In file included from /opt/homebrew/include/wx-3.2/wx/wx.h:24:
In file included from /opt/homebrew/include/wx-3.2/wx/event.h:22:
In file included from /opt/homebrew/include/wx-3.2/wx/cursor.h:75:
/opt/homebrew/include/wx-3.2/wx/utils.h:749:35: warning: default member initializer for non-s
tatic data member is a C++11 extension [-Wc++11-extensions]
    wxEventLoop* m_modalEventLoop = NULL;
                                  ^
1 warning generated.
ld: Undefined symbols:
  wxEntry(int&, char**), referenced from:
      _main in conftest-610236.o
  wxTextAttr::Init(), referenced from:
      wxTextAttr::wxTextAttr() in conftest-610236.o
  wxStopWatch::Start(long), referenced from:
      wxStyledTextCtrl::wxStyledTextCtrl() in conftest-610236.o
  wxEvtHandler::QueueEvent(wxEvent*), referenced from:
      vtable for MyApp in conftest-610236.o

I suspect these undefined-symbol errors prevent building wxe_driver.so file.

Workaround

Adding -undefined suppress to the linker flag during the configuration testing phase will suppress the error, although this is not a fix of root cause.

See https://github.com/erlang/otp/compare/OTP-26.1...jj1bdx:otp:jj1bdx-otp-26.1-macOS-wx-fix?expand=1 for the diff with OTP-26.1. With this diff, the wx is successfully built and running with OTP-26.1 on macOS.

Thoughts

I am sure that this is not really a fix, and I don't know much about macOS linker issues. I hope Björn and OTP Team would deliver a much better fix than this.

[bjorng]

Thanks! I have pushed a fixup commit.

It turns out that the linker test was broken when only dynamic wx libraries were available; no list of ws libraries would be given to the linker. The -undefined warning option that was used before this PR hid the bug by suppressing the errors for the undefined functions.

[jj1bdx]

@bjorng bd01a1c worked fine here and wx was successfully invoked and running. Many thanks!