Remove -static-libgcc link flag from mingw32 port (#1535)

* MPR#6411 revisited

Including -static-libgcc in all link instructions prevents C++ exceptions
from ever working. mmap.o is the only affected unit, since it needs
auxiliary functions to perform division of an __int64. A better fix is to
specify --static-libgcc only when building dllbigarray.dll and dllunix.dll
(since they both export versions of this primitive).

* Correct -static-libgcc error in README.win32.adoc

The instructions for the mingw64 port added in 600a93d amended the
sentence about -static-libgcc to include config/Makefile.mingw64. The
64-bit mingw port has never required or included this flag.

Changes

@@ -82,6 +82,11 @@ Working version
 
 ### Runtime system:
 
+- MPR#6411, GPR#1535: don't compile everything with -static-libgcc on mingw32,
+  only dllbigarray.dll and libbigarray.a. Allows the use of C++ libraries which
+  raise exceptions.
+  (David Allsopp)
+
 - GPR#1431: remove ocamlrun dependencies on curses/terminfo/termcap C library
   (Xavier Leroy, review by Daniel Bünzli)
 

README.win32.adoc

@@ -294,12 +294,6 @@ bash or by adding Cygwin's bin directory (e.g. `C:\cygwin\bin`) to your `PATH`.
 
 * The replay debugger is partially supported (no reverse execution).
 
-* The default `config/Makefile.mingw` and `config/Makefile.mingw64` pass
-  `-static-libgcc` to the linker. For more information on this topic:
-
-  - http://gcc.gnu.org/onlinedocs/gcc-4.9.1/gcc/Link-Options.html#Link-Options
-  - http://caml.inria.fr/mantis/view.php?id=6411
-
 [[seflexdll]]
 == FlexDLL
 Although the core of FlexDLL is necessarily written in C, the `flexlink` program

config/Makefile.mingw

@@ -133,7 +133,7 @@ FLEXLINK_CMD=flexlink
 FLEXDLL_CHAIN=mingw
 # FLEXLINK_FLAGS must be safe to insert in an OCaml string
 #   (see ocamlmklibconfig.ml in tools/Makefile)
-FLEXLINK_FLAGS=-chain $(FLEXDLL_CHAIN) -stack 16777216 -link -static-libgcc
+FLEXLINK_FLAGS=-chain $(FLEXDLL_CHAIN) -stack 16777216
 FLEXLINK=$(FLEXLINK_CMD) $(FLEXLINK_FLAGS)
 FLEXDIR:=$(shell $(FLEXLINK) -where 2>/dev/null)
 ifeq ($(FLEXDIR),)

otherlibs/bigarray/Makefile

@@ -21,6 +21,10 @@ CAMLOBJS=bigarray.cmo
 
 include ../Makefile
 
+ifeq "$(SYSTEM)" "mingw"
+LDOPTS=-ldopt "-link -static-libgcc"
+endif
+
 mmap.$(O): ../$(UNIXLIB)/mmap.c
 	$(CC) -c $(CFLAGS) $(CPPFLAGS) $(OUTPUTOBJ)$@ $<
 mmap_ba.$(O): ../unix/mmap_ba.c

otherlibs/win32unix/Makefile

@@ -39,14 +39,12 @@ UNIX_FILES = access.c addrofstr.c chdir.c chmod.c cst2constr.c \
 UNIX_CAML_FILES = unix.mli unixLabels.mli unixLabels.ml
 
 ALL_FILES=$(WIN_FILES) $(UNIX_FILES)
-WSOCKLIB=$(call SYSLIB,ws2_32)
-ADVAPI32LIB=$(call SYSLIB,advapi32)
 
 LIBNAME=unix
 COBJS=$(ALL_FILES:.c=.$(O))
 CAMLOBJS=unix.cmo unixLabels.cmo
-LINKOPTS=-cclib $(WSOCKLIB) -cclib $(ADVAPI32LIB)
-LDOPTS=-ldopt $(WSOCKLIB) -ldopt $(ADVAPI32LIB)
+WIN32_LIBS=$(call SYSLIB,ws2_32) $(call SYSLIB,advapi32)
+LINKOPTS=$(addprefix -cclib ,$(WIN32_LIBS))
 EXTRACAMLFLAGS=-nolabels
 EXTRACFLAGS=-I../unix
 HEADERS=unixsupport.h socketaddr.h
@@ -54,6 +52,12 @@ HEADERS=unixsupport.h socketaddr.h
 
 include ../Makefile
 
+ifeq "$(SYSTEM)" "mingw"
+LDOPTS=-ldopt "-link -static-libgcc" $(addprefix -ldopt ,$(WIN32_LIBS))
+else
+LDOPTS=$(addprefix -ldopt ,$(WIN32_LIBS))
+endif
+
 clean::
 	rm -f $(UNIX_FILES) $(UNIX_CAML_FILES)