configure: support --enable-glibgxx-debug

Part of #184.

* m4/devel.m4 (adl_ENABLE_GLIBCXX_DEBUG): New macro.
* configure.ac: Use it.
* README: Mention it.
* spot/twa/acc.cc: Fix a small issue found with this
option.

README

@@ -87,6 +87,14 @@ flags specific to Spot:
       --disable-assert
       --enable-optimizations
 
+   --enable-glibgxx-debug
+     Enable the debugging version libstdc++
+     https://gcc.gnu.org/onlinedocs/libstdc++/manual/debug_mode_semantics.html
+     Note that the debugging version og libstdc++ is incompatible with
+     the regular version.  So if Spot is compiled with this option, all
+     client code should be compiled with -D_GLIBCXX_DEBUG as well.  This
+     options should normally only be useful to run Spot's test-suite.
+
 Here are the meaning of the fine-tuning options, in case
 --enable/disable-devel is not enough.
 

configure.ac

@@ -145,6 +145,7 @@ fi
 adl_ENABLE_DEBUG
 ad_GCC_OPTIM
 adl_NDEBUG
+adl_ENABLE_GLIBCXX_DEBUG
 
 spot_INTEL
 if test x$enable_warnings = xyes; then

m4/devel.m4

@@ -27,3 +27,13 @@ AC_DEFUN([adl_ENABLE_DEVEL],
    enable_optimizations=${enable_optimizations--O}
  fi
 ])
+
+
+AC_DEFUN([adl_ENABLE_GLIBCXX_DEBUG],
+[AC_ARG_ENABLE([glibcxx-debug],
+  [AC_HELP_STRING([--enable-glibcxx-debug],
+    [turn on use the libstdc++ debug mode (see README)])])
+if test x$enable_glibcxx_debug = xyes; then
+  CPPFLAGS="$CPPFLAGS -D_GLIBCXX_DEBUG"
+fi
+])

spot/twa/acc.cc

@@ -574,6 +574,7 @@ namespace spot
       {
         // Pick a random code and put it at the end
         int p1 = mrand(s--);
+        if (p1 != s) // https://gcc.gnu.org/bugzilla//show_bug.cgi?id=59603
           std::swap(codes[p1], codes[s]);
         // and another one
         int p2 = mrand(s);