# Minimum warning options... any contributions to OpenSSL should at least get
# past these.
-my $gcc_devteam_warn = "-Wall -pedantic -DPEDANTIC -Wno-long-long -Wsign-compare -Wmissing-prototypes -Wshadow -Wformat -Werror -DCRYPTO_MDEBUG_ALL -DCRYPTO_MDEBUG_ABORT -DREF_CHECK -DOPENSSL_NO_DEPRECATED";
+my $gcc_devteam_warn = "-Wall -pedantic -DPEDANTIC -Wno-long-long -Wsign-compare -Wmissing-prototypes -Wshadow -Wformat -Wundef -Werror -DCRYPTO_MDEBUG_ALL -DCRYPTO_MDEBUG_ABORT -DREF_CHECK -DOPENSSL_NO_DEPRECATED";
# TODO(openssl-team): fix problems and investigate if (at least) the following
# warnings can also be enabled: