cgraph: autotools: add definition of export symbols

Fixes errors like this with MinGW:

lib\cgraph/apply.c:48: undefined reference to `__imp_agfstsubg'

Towards https://gitlab.com/graphviz/graphviz/-/issues/2058

diff --git a/lib/cgraph/Makefile.am b/lib/cgraph/Makefile.am
index 835315d2c81d480c2188877e7669f6106466e596..39e1ff0cac6b0d86c6d67ccd7a5132829fc4566a 100644 (file)
--- a/lib/cgraph/Makefile.am
+++ b/lib/cgraph/Makefile.am
@@ -7,6 +7,10 @@ pkgconfigdir = $(libdir)/pkgconfig
 
 AM_CPPFLAGS = -I$(top_srcdir)/lib -I$(top_srcdir)/lib/cdt
 
+if WITH_WIN32
+AM_CFLAGS = -DEXPORT_CGRAPH -DEXPORT_AGXBUF -DEXPORT_CGHDR
+endif
+
 pkginclude_HEADERS = cgraph.h
 noinst_HEADERS = agxbuf.h cghdr.h itos.h likely.h prisize_t.h sprint.h \
   strcasecmp.h unreachable.h