[Libguestfs] [PATCH nbdkit] build: Use dlsym as sentinel function for -ldl.

When testing which “dl library” we must use for dl* symbols, autoconf runs a test similar to: $ cat conftest.c char dlopen (); int main () { return dlopen (); } $ gcc -o conftest $CFLAGS conftest.c [try various -ldl options here] When using ‘CFLAGS="-fsanitize=address"’ this succeeds even if no dl libraries are used at all, since it appears that using this option causes dlopen to be included in the final binary implicitly. This causes configure to set DL_LIBS='', but unfortunately dlsym is not included implicitly and so linking fails. Although I believe this is a bug in GCC 9, as a workaround use dlsym as the sentinel function instead. The new output from ‘./configure CFLAGS="-fsanitize=address"’ is: checking for library containing dlsym... -ldl [...] checking for dladdr... yes See also: https://bugzilla.redhat.com/show_bug.cgi?id=1702761 --- configure.ac | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/configure.ac b/configure.ac index 4624bf8..1d3aa7b 100644 --- a/configure.ac +++ b/configure.ac @@ -224,11 +224,11 @@ AS_IF([test "x$nbdkit_cv_func_printf_percent_m" = xyes], [Define to 1 if vfprintf supports %m.])]) old_LIBS="$LIBS" -AC_SEARCH_LIBS([dlopen], [dl dld], [ - AS_IF([test "x$ac_cv_search_dlopen" != "xnone required"], - [DL_LIBS="$ac_cv_search_dlopen"], [DL_LIBS=]) +AC_SEARCH_LIBS([dlsym], [dl dld], [ + AS_IF([test "x$ac_cv_search_dlsym" != "xnone required"], + [DL_LIBS="$ac_cv_search_dlsym"], [DL_LIBS=]) AC_SUBST([DL_LIBS]) - ], [AC_MSG_ERROR([unable to find the dlopen() function]) + ], [AC_MSG_ERROR([unable to find the dlsym() function]) ]) LIBS="$old_LIBS" -- 2.20.1