Build with -fvisibility=hidden when supported

ChangeLog

@@ -1,5 +1,15 @@
 2019-06-21  Jay Berkenbilt  <ejb@ql.org>
 
+	* When supported, qpdf builds with -fvisibility=hidden, which
+	removes non-exported symbols from the shared library in a manner
+	similar to how Windows DLLs work. This is better for performance
+	and also better for safety and protection of private interfaces.
+	See https://gcc.gnu.org/wiki/Visibility. *NOTE*: If you are
+	getting linker errors trying to catch exceptions or derive things
+	from a base class in the qpdf library, it's possible that a
+	QPDF_DLL_CLASS declaration is missing somewhere. Please report
+	this as a bug at https://github.com/qpdf/qpdf/issues.
+
 	* Source-level incompatibility: remove the version
 	QPDF::copyForeignObject with an unused boolean parameter. If you
 	were, for some reason, calling this, just take the parameter away.

README-maintainer

@@ -64,6 +64,12 @@ CODING RULES
 
 * Use QIntC for type conversions -- see casting policy in docs.
 
+* Use QPDF_DLL on all methods that are to be exported in the shared
+  library/DLL. Use QPDF_DLL_CLASS for all classes whose type
+  information is needed. This is important for exception classes and
+  it seems also for classes that are intended to be subclassed across
+  the shared library boundary.
+
 RELEASE PREPARATION
 
 * Each year, update copyright notices. Just do a case-insensitive

TODO

@@ -1,9 +1,6 @@
 Next ABI
 ========
 
- * Build with -fvisibility=hidden by default. Fix QPDF_DLL. See #302
-   for discussion. See also https://gcc.gnu.org/wiki/Visibility
-
  * Check all classes that don't use the Members pattern and see if
    they should be converted. Most of the pipeline classes should be
    converted.

autofiles.sums

@@ -1,4 +1,4 @@
-3bb3daeee89ecd7770434a3357d2f4bd6ad415de8cdacc90d5e1fce39e1b3a91  configure.ac
+5b50c329677bcc8c1d5a8b3654b79ccca8bbe80a452cc4bb14938370f316327a  configure.ac
 35bc5c645dc42d47f2daeea06f8f3e767c8a1aee6a35eb2b4854fd2ce66c3413  m4/ax_random_device.m4
 37f8897d5f68d7d484e5457832a8f190ddb7507fa2a467cb7ee2be40a4364643  m4/libtool.m4
 e77ebba8361b36f14b4d0927173a034b98c5d05049697a9ded84d85eb99a7990  m4/ltoptions.m4

configure

@@ -15840,6 +15840,61 @@ LT_REVISION=2
 LT_SONAME=$(expr $LT_CURRENT - $LT_AGE)
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -fvisibility=hidden" >&5
+$as_echo_n "checking for -fvisibility=hidden... " >&6; }
+try_flags=-fvisibility=hidden
+oCXXFLAGS=$CXXFLAGS
+CXXFLAGS="$CXXFLAGS $try_flags"
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+class X
+{
+  public:
+    __attribute__ ((visibility ("default")))
+    X() {}
+    __attribute__ ((visibility ("default")))
+    void f() {}
+};
+
+int
+main ()
+{
+X x; x.f();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  qpdf_VISIBILITY_HIDDEN=1
+else
+  qpdf_VISIBILITY_HIDDEN=0
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$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
+
+if test "$qpdf_VISIBILITY_HIDDEN" = "0"; then
+   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+   CXXFLAGS=$oCXXFLAGS
+else
+   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+   CFLAGS="$CFLAGS $try_flags"
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to use insecure random numbers" >&5
+$as_echo_n "checking whether to use insecure random numbers... " >&6; }
 # Check whether --enable-insecure-random was given.
 if test "${enable_insecure_random+set}" = set; then :
   enableval=$enable_insecure_random; if test "$enableval" = "yes"; then

configure.ac

@@ -60,6 +60,33 @@ AC_SUBST(LT_AGE)
 LT_SONAME=$(expr $LT_CURRENT - $LT_AGE)
 AC_SUBST(LT_SONAME)
 
+AC_MSG_CHECKING(for -fvisibility=hidden)
+try_flags=-fvisibility=hidden
+oCXXFLAGS=$CXXFLAGS
+CXXFLAGS="$CXXFLAGS $try_flags"
+AC_LANG_PUSH([C++])
+AC_LINK_IFELSE([AC_LANG_PROGRAM(
+    [[class X
+{
+  public:
+    __attribute__ ((visibility ("default")))
+    X() {}
+    __attribute__ ((visibility ("default")))
+    void f() {}
+};
+   ]],[[X x; x.f();]])],
+   [qpdf_VISIBILITY_HIDDEN=1],
+   [qpdf_VISIBILITY_HIDDEN=0])
+AC_LANG_POP
+if test "$qpdf_VISIBILITY_HIDDEN" = "0"; then
+   AC_MSG_RESULT(no)
+   CXXFLAGS=$oCXXFLAGS
+else
+   AC_MSG_RESULT(yes)
+   CFLAGS="$CFLAGS $try_flags"
+fi
+
+AC_MSG_CHECKING(whether to use insecure random numbers)
 AC_ARG_ENABLE(insecure-random,
    AS_HELP_STRING([--enable-insecure-random],
                   [whether to use stdlib's random number generator (default is no)]),

include/qpdf/DLL.h

@@ -23,15 +23,15 @@
 #ifndef QPDF_DLL_HH
 #define QPDF_DLL_HH
 
-#if defined(_WIN32) && defined(DLL_EXPORT)
+#if (defined _WIN32 || defined __CYGWIN__) && defined(DLL_EXPORT)
 # define QPDF_DLL __declspec(dllexport)
-# define QPDF_DLL_EXCEPTION
+# define QPDF_DLL_CLASS
 #elif __GNUC__ >= 4
 # define QPDF_DLL __attribute__ ((visibility ("default")))
-# define QPDF_DLL_EXCEPTION __attribute__ ((visibility ("default")))
+# define QPDF_DLL_CLASS __attribute__ ((visibility ("default")))
 #else
 # define QPDF_DLL
-# define QPDF_DLL_EXCEPTION
+# define QPDF_DLL_CLASS
 #endif
 
 #endif /* QPDF_DLL_HH */

include/qpdf/InputSource.hh

@@ -27,7 +27,7 @@
 #include <stdio.h>
 #include <string>
 
-class InputSource
+class QPDF_DLL_CLASS InputSource
 {
   public:
     QPDF_DLL
@@ -40,7 +40,7 @@ class InputSource
     {
     }
 
-    class Finder
+    class QPDF_DLL_CLASS Finder
     {
       public:
         Finder()

include/qpdf/Pipeline.hh

@@ -47,7 +47,7 @@
 #include <qpdf/DLL.h>
 #include <string>
 
-class Pipeline
+class QPDF_DLL_CLASS Pipeline
 {
   public:
     QPDF_DLL

include/qpdf/Pl_DCT.hh

@@ -33,7 +33,7 @@ class Pl_DCT: public Pipeline
     QPDF_DLL
     Pl_DCT(char const* identifier, Pipeline* next);
 
-    class CompressConfig
+    class QPDF_DLL_CLASS CompressConfig
     {
       public:
         CompressConfig()

include/qpdf/QPDFExc.hh

@@ -29,7 +29,7 @@
 #include <string>
 #include <stdexcept>
 
-class QPDF_DLL_EXCEPTION QPDFExc: public std::runtime_error
+class QPDF_DLL_CLASS QPDFExc: public std::runtime_error
 {
   public:
     QPDF_DLL

include/qpdf/QPDFObjectHandle.hh

@@ -54,7 +54,7 @@ class QPDFObjectHandle
     // alternative way of associating stream data with a stream.  See
     // comments on replaceStreamData and newStream for additional
     // details.
-    class StreamDataProvider
+    class QPDF_DLL_CLASS StreamDataProvider
     {
       public:
 	QPDF_DLL
@@ -99,7 +99,7 @@ class QPDFObjectHandle
     // string token will also work. The correct way to construct a
     // string token that would write the literal value (str) is
     // QPDFTokenizer::Token(QPDFTokenizer::tt_string, "str").
-    class TokenFilter
+    class QPDF_DLL_CLASS TokenFilter
     {
       public:
         QPDF_DLL

include/qpdf/QPDFSystemError.hh

@@ -29,7 +29,7 @@
 #include <string>
 #include <stdexcept>
 
-class QPDF_DLL_EXCEPTION QPDFSystemError: public std::runtime_error
+class QPDF_DLL_CLASS QPDFSystemError: public std::runtime_error
 {
   public:
     QPDF_DLL

include/qpdf/QPDFWriter.hh

@@ -76,7 +76,7 @@ class QPDFWriter
     QPDF_DLL
     ~QPDFWriter();
 
-    class ProgressReporter
+    class QPDF_DLL_CLASS ProgressReporter
     {
       public:
         virtual ~ProgressReporter()

include/qpdf/RandomDataProvider.hh

@@ -22,9 +22,10 @@
 #ifndef RANDOMDATAPROVIDER_HH
 #define RANDOMDATAPROVIDER_HH
 
+#include <qpdf/DLL.h>
 #include <string.h> // for size_t
 
-class RandomDataProvider
+class QPDF_DLL_CLASS RandomDataProvider
 {
   public:
     virtual ~RandomDataProvider()