autotools: Add --no-undefined linker option

Makefile.am

@@ -98,7 +98,7 @@ endif
 libsecp256k1_la_SOURCES = src/secp256k1.c
 libsecp256k1_la_CPPFLAGS = $(SECP_CONFIG_DEFINES)
 libsecp256k1_la_LIBADD = $(COMMON_LIB) $(PRECOMPUTED_LIB)
-libsecp256k1_la_LDFLAGS = -no-undefined -version-info $(LIB_VERSION_CURRENT):$(LIB_VERSION_REVISION):$(LIB_VERSION_AGE)
+libsecp256k1_la_LDFLAGS = -no-undefined -version-info $(LIB_VERSION_CURRENT):$(LIB_VERSION_REVISION):$(LIB_VERSION_AGE) $(SECP_LIB_LDFLAGS)
 
 noinst_PROGRAMS =
 if USE_BENCHMARK

build-aux/m4/bitcoin_secp.m4

@@ -77,6 +77,22 @@ AC_DEFUN([SECP_TRY_APPEND_CFLAGS], [
   AC_SUBST($2)
 ])
 
+dnl SECP_TRY_APPEND_LDFLAGS(flags, VAR)
+dnl Append flags to VAR if a linker accepts them.
+AC_DEFUN([SECP_TRY_APPEND_LDFLAGS], [
+  AC_MSG_CHECKING([if linker supports $1])
+  SECP_TRY_APPEND_LDFLAGS_saved_LDFLAGS="$LDFLAGS"
+  LDFLAGS="$1 $LDFLAGS"
+  AC_LINK_IFELSE([AC_LANG_PROGRAM()], [flag_works=yes], [flag_works=no])
+  AC_MSG_RESULT($flag_works)
+  LDFLAGS="$SECP_TRY_APPEND_LDFLAGS_saved_LDFLAGS"
+  if test x"$flag_works" = x"yes"; then
+    $2="$$2 $1"
+  fi
+  unset flag_works
+  AC_SUBST($2)
+])
+
 dnl SECP_SET_DEFAULT(VAR, default, default-dev-mode)
 dnl Set VAR to default or default-dev-mode, depending on whether dev mode is enabled
 AC_DEFUN([SECP_SET_DEFAULT], [

configure.ac

@@ -420,6 +420,8 @@ fi
 
 if test x"$enable_external_default_callbacks" = x"yes"; then
   SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DUSE_EXTERNAL_DEFAULT_CALLBACKS=1"
+else
+  SECP_TRY_APPEND_LDFLAGS([-Wl,--no-undefined], [SECP_LIB_LDFLAGS])
 fi
 
 ###
@@ -486,6 +488,7 @@ echo "  CC                      = $CC"
 echo "  CPPFLAGS                = $CPPFLAGS"
 echo "  SECP_CFLAGS             = $SECP_CFLAGS"
 echo "  CFLAGS                  = $CFLAGS"
+echo "  SECP_LIB_LDFLAGS        = $SECP_LIB_LDFLAGS"
 echo "  LDFLAGS                 = $LDFLAGS"
 
 if test x"$print_msan_notice" = x"yes"; then