+dnl Only add the -lm library if floating point functions cannot be used
+dnl without it. This check is important on cygwin because of the bizarre
+dnl way that they have organized functions into libraries. On cygwin, both
+dnl libc.a and libm.a are symbolic links to a single lib libcygwin.a. This
+dnl means that
+dnl 1) linking with -lm is not necessary, and
+dnl 2) linking with -lm is dangerous if the order of libraries is wrong
+dnl In particular, if you compile any program with -mno-cygwin and link with
+dnl -lm, it will crash instantly when it is run. This happens because the
+dnl linker incorrectly links the Cygwin libm.a (==libcygwin.a), which replaces
+dnl the ___main function instead of allowing it to be defined by
+dnl /usr/lib/mingw/libmingw32.a as it should be.
+dnl
+dnl On MacOS X, this test will find that -lm is unnecessary and leave it out.
+dnl
+dnl Just check a few floating point functions. If they are all found without
+dnl -lm, then we must not need -lm.
+have_cos=0
+have_floor=0
+AC_CHECK_FUNCS(cos, have_cos=1)
+AC_CHECK_FUNCS(floor, have_floor=1)
+AC_MSG_CHECKING(if floating point functions link without -lm)
+if test "$have_cos" = 1 -a "$have_floor" = 1; then
+ AC_MSG_RESULT(yes)
+else
+ AC_MSG_RESULT(no)
+ LIBS="$LIBS -lm"
+ # use different functions to avoid configure caching
+ have_sin=0
+ have_ceil=0
+ AC_CHECK_FUNCS(sin, have_sin=1)
+ AC_CHECK_FUNCS(ceil, have_ceil=1)
+ AC_MSG_CHECKING(if floating point functions link with -lm)
+ if test "$have_sin" = 1 -a "$have_ceil" = 1; then
+ AC_MSG_RESULT(yes)
+ else
+ AC_MSG_RESULT(no)
+ # not sure we should warn the user, crash, etc.
+ fi
+fi
+
projects / wxWidgets.git / blobdiff