lib: rework how we "override" assert()

The previous method, using zassert.h and hoping nothing includes
assert.h (which, on glibc at least, just does "#undef assert" and puts
its own definition in...) was fragile - and actually broke undetected.

Just provide our own assert.h and control overriding by putting it in a
separate directory to add to the include path (or not.)

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

Makefile.am

@@ -11,11 +11,19 @@ AM_CFLAGS = \
 	$(SAN_FLAGS) \
 	$(WERROR) \
 	# end
-AM_CPPFLAGS = \
+
+# CPPFLAGS_BASE does not contain the include path for overriding assert.h,
+# therefore should be used in tools that do *not* link libfrr or do not want
+# assert() overridden
+CPPFLAGS_BASE = \
 	-I$(top_srcdir) -I$(top_srcdir)/include -I$(top_srcdir)/lib \
 	-I$(top_builddir) \
 	$(LUA_INCLUDE) \
 	# end
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/lib/assert \
+	$(CPPFLAGS_BASE) \
+	# end
 AM_LDFLAGS = \
 	-export-dynamic \
 	$(AC_LDFLAGS) \

lib/assert/assert.h

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2021  David Lamparter, for NetDEF, Inc.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* WARNING: this file is "special" in that it overrides the system-provided
+ * assert.h by being on the include path before it.  That means it should
+ * provide the functional equivalent.
+ *
+ * This is intentional because FRR extends assert() to write to the log and
+ * add backtraces.  Overriding the entire file is the simplest and most
+ * reliable way to get this to work;  there were problems previously with the
+ * system assert.h getting included afterwards and redefining assert() back to
+ * the system variant.
+ */
+
+#ifndef _FRR_ASSERT_H
+#define _FRR_ASSERT_H
+
+#include "xref.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef __cplusplus
+/* C++ has this built-in, but C provides it in assert.h for >=C11.  Since we
+ * replace assert.h entirely, we need to provide it here too.
+ */
+#define static_assert _Static_assert
+#endif
+
+struct xref_assert {
+	struct xref xref;
+
+	const char *expr;
+	const char *extra, *args;
+};
+
+extern void _zlog_assert_failed(const struct xref_assert *xref,
+				const char *extra, ...) PRINTFRR(2, 3)
+	__attribute__((noreturn));
+
+/* the "do { } while (expr_)" is there to get a warning for assignments inside
+ * the assert expression aka "assert(x = 1)".  The (necessary) braces around
+ * expr_ in the if () statement would suppress these warnings.  Since
+ * _zlog_assert_failed() is noreturn, the while condition will never be
+ * checked.
+ */
+#define assert(expr_)                                                          \
+	({                                                                     \
+		static const struct xref_assert _xref __attribute__(           \
+			(used)) = {                                            \
+			.xref = XREF_INIT(XREFT_ASSERT, NULL, __func__),       \
+			.expr = #expr_,                                        \
+		};                                                             \
+		XREF_LINK(_xref.xref);                                         \
+		if (__builtin_expect((expr_) ? 0 : 1, 0))                      \
+			do {                                                   \
+				_zlog_assert_failed(&_xref, NULL);             \
+			} while (expr_);                                       \
+	})
+
+#define assertf(expr_, extra_, ...)                                            \
+	({                                                                     \
+		static const struct xref_assert _xref __attribute__(           \
+			(used)) = {                                            \
+			.xref = XREF_INIT(XREFT_ASSERT, NULL, __func__),       \
+			.expr = #expr_,                                        \
+			.extra = extra_,                                       \
+			.args = #__VA_ARGS__,                                  \
+		};                                                             \
+		XREF_LINK(_xref.xref);                                         \
+		if (__builtin_expect((expr_) ? 0 : 1, 0))                      \
+			do {                                                   \
+				_zlog_assert_failed(&_xref, extra_,            \
+						    ##__VA_ARGS__);            \
+			} while (expr_);                                       \
+	})
+
+#define zassert assert
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _FRR_ASSERT_H */

lib/clippy.c

@@ -115,15 +115,6 @@ void vzlogx(const struct xref_logmsg *xref, int prio,
 	fputs("\n", stderr);
 }
 
-void _zlog_assert_failed(const char *assertion, const char *file,
-			 unsigned int line, const char *function)
-{
-	fprintf(stderr,
-		"Assertion `%s' failed in file %s, line %u, function %s",
-		assertion, file, line, (function ? function : "?"));
-	abort();
-}
-
 void memory_oom(size_t size, const char *name)
 {
 	abort();

lib/log.c

@@ -311,17 +311,6 @@ void zlog_thread_info(int log_level)
 		zlog(log_level, "Current thread not known/applicable");
 }
 
-void _zlog_assert_failed(const char *assertion, const char *file,
-			 unsigned int line, const char *function)
-{
-	zlog(LOG_CRIT, "Assertion `%s' failed in file %s, line %u, function %s",
-	     assertion, file, line, (function ? function : "?"));
-	zlog_backtrace(LOG_CRIT);
-	zlog_thread_info(LOG_CRIT);
-	log_memstats(stderr, "log");
-	abort();
-}
-
 void memory_oom(size_t size, const char *name)
 {
 	zlog(LOG_CRIT,

lib/subdir.am

@@ -284,6 +284,8 @@ pkginclude_HEADERS += \
 	lib/zlog_targets.h \
 	lib/pbr.h \
 	lib/routing_nb.h \
+	\
+	lib/assert/assert.h \
 	# end
 
 
@@ -412,7 +414,7 @@ lib_grammar_sandbox_SOURCES = \
 lib_grammar_sandbox_LDADD = \
 	lib/libfrr.la
 
-lib_clippy_CPPFLAGS = $(AM_CPPFLAGS) -D_GNU_SOURCE -DBUILDING_CLIPPY
+lib_clippy_CPPFLAGS = $(CPPFLAGS_BASE) -D_GNU_SOURCE -DBUILDING_CLIPPY
 lib_clippy_CFLAGS = $(AC_CFLAGS) $(PYTHON_CFLAGS)
 lib_clippy_LDADD = $(PYTHON_LIBS) $(UST_LIBS) -lelf
 lib_clippy_LDFLAGS = -export-dynamic

lib/xref.h

@@ -33,6 +33,7 @@ enum xref_type {
 	XREFT_THREADSCHED = 0x100,
 
 	XREFT_LOGMSG = 0x200,
+	XREFT_ASSERT = 0x280,
 
 	XREFT_DEFUN = 0x300,
 	XREFT_INSTALL_ELEMENT = 0x301,

lib/zlog.c

@@ -521,6 +521,36 @@ void zlog_sigsafe(const char *text, size_t len)
 	}
 }
 
+void _zlog_assert_failed(const struct xref_assert *xref, const char *extra, ...)
+{
+	va_list ap;
+	static bool assert_in_assert; /* "global-ish" variable, init to 0 */
+
+	if (assert_in_assert)
+		abort();
+	assert_in_assert = true;
+
+	if (extra) {
+		struct va_format vaf;
+
+		va_start(ap, extra);
+		vaf.fmt = extra;
+		vaf.va = ≈
+
+		zlog(LOG_CRIT,
+		     "%s:%d: %s(): assertion (%s) failed, extra info: %pVA",
+		     xref->xref.file, xref->xref.line, xref->xref.func,
+		     xref->expr, &vaf);
+
+		va_end(ap);
+	} else
+		zlog(LOG_CRIT, "%s:%d: %s(): assertion (%s) failed",
+		     xref->xref.file, xref->xref.line, xref->xref.func,
+		     xref->expr);
+
+	/* abort() prints backtrace & memstats in SIGABRT handler */
+	abort();
+}
 
 int zlog_msg_prio(struct zlog_msg *msg)
 {

tests/.gitignore

@@ -21,6 +21,7 @@
 /lib/cli/test_commands_defun.c
 /lib/northbound/test_oper_data
 /lib/cxxcompat
+/lib/test_assert
 /lib/test_atomlist
 /lib/test_buffer
 /lib/test_checksum
@@ -52,4 +53,4 @@
 /lib/test_zmq
 /ospf6d/test_lsdb
 /ospf6d/test_lsdb_clippy.c
-/zebra/test_lm_plugin
+/zebra/test_lm_plugin

tests/lib/test_assert.c

@@ -0,0 +1,64 @@
+/*
+ * Quick test for assert()
+ * Copyright (C) 2021  David Lamparter for NetDEF, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+/* make sure this works with assert.h & nothing else.  also check the include
+ * shadowing, we don't want to pick up system assert.h
+ */
+#include <assert.h>
+
+__attribute__((noinline))
+void func_for_bt(int number)
+{
+	assert(number > 2);
+	assertf(number > 3, "(A) the number was %d", number);
+}
+
+#include <zebra.h>
+#include "lib/zlog.h"
+#include "lib/thread.h"
+#include "lib/sigevent.h"
+
+int main(int argc, char **argv)
+{
+	int number = 10;
+	struct thread_master *master;
+
+	zlog_aux_init("NONE: ", LOG_DEBUG);
+
+	if (argc > 1)
+		number = atoi(argv[1]);
+
+	assert(number > 0);
+	assertf(number > 1, "(B) the number was %d", number);
+
+	/* set up SIGABRT handler */
+	master = thread_master_create("test");
+	signal_init(master, 0, NULL);
+
+	func_for_bt(number);
+	assert(number > 4);
+	assertf(number > 5, "(C) the number was %d", number);
+
+	assertf(number > 10, "(D) the number was %d", number);
+	return 0;
+}

tests/lib/test_assert.py

@@ -0,0 +1,56 @@
+import frrtest
+import os
+import re
+import subprocess
+import inspect
+
+basedir = os.path.dirname(__file__)
+program = os.path.join(basedir, "test_assert")
+
+
+def check(number, rex=None):
+    proc = subprocess.Popen(
+        [frrtest.binpath(program), str(number)],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+    )
+    out, err = proc.communicate()
+    exitcode = proc.wait()
+
+    if rex is None:
+        assert exitcode == 0
+    else:
+        assert exitcode != 0
+
+        text = out.decode("US-ASCII") + err.decode("US-ASCII")
+        rex = re.compile(rex, re.M | re.S)
+        m = rex.search(text)
+        assert m is not None, "non-matching output: %s" % text
+
+
+def test_assert_0():
+    check(0, r"test_assert\.c:\d+.*number > 0")
+
+
+def test_assert_1():
+    check(1, r"test_assert\.c:\d+.*number > 1.*\(B\) the number was 1")
+
+
+def test_assert_2():
+    check(2, r"test_assert\.c:\d+.*number > 2")
+
+
+def test_assert_3():
+    check(3, r"test_assert\.c:\d+.*number > 3.*\(A\) the number was 3")
+
+
+def test_assert_4():
+    check(4, r"test_assert\.c:\d+.*number > 4")
+
+
+def test_assert_10():
+    check(10, r"test_assert\.c:\d+.*number > 10.*\(D\) the number was 10")
+
+
+def test_assert_11():
+    check(11)

tests/subdir.am

@@ -66,6 +66,7 @@ clippy_scan += \
 
 check_PROGRAMS = \
 	tests/lib/cxxcompat \
+	tests/lib/test_assert \
 	tests/lib/test_atomlist \
 	tests/lib/test_buffer \
 	tests/lib/test_checksum \
@@ -249,6 +250,10 @@ tests_lib_northbound_test_oper_data_CPPFLAGS = $(TESTS_CPPFLAGS)
 tests_lib_northbound_test_oper_data_LDADD = $(ALL_TESTS_LDADD)
 tests_lib_northbound_test_oper_data_SOURCES = tests/lib/northbound/test_oper_data.c
 nodist_tests_lib_northbound_test_oper_data_SOURCES = yang/frr-test-module.yang.c
+tests_lib_test_assert_CFLAGS = $(TESTS_CFLAGS)
+tests_lib_test_assert_CPPFLAGS = $(TESTS_CPPFLAGS)
+tests_lib_test_assert_LDADD = $(ALL_TESTS_LDADD)
+tests_lib_test_assert_SOURCES = tests/lib/test_assert.c
 tests_lib_test_atomlist_CFLAGS = $(TESTS_CFLAGS)
 tests_lib_test_atomlist_CPPFLAGS = $(TESTS_CPPFLAGS)
 tests_lib_test_atomlist_LDADD = $(ALL_TESTS_LDADD)
@@ -404,6 +409,7 @@ EXTRA_DIST += \
 	tests/lib/northbound/test_oper_data.in \
 	tests/lib/northbound/test_oper_data.py \
 	tests/lib/northbound/test_oper_data.refout \
+	tests/lib/test_assert.py \
 	tests/lib/test_atomlist.py \
 	tests/lib/test_nexthop_iter.py \
 	tests/lib/test_ntop.py \

tools/subdir.am

@@ -34,9 +34,11 @@ tools_gen_yang_deviations_SOURCES = tools/gen_yang_deviations.c
 tools_gen_yang_deviations_LDADD = lib/libfrr.la $(LIBYANG_LIBS)
 
 tools_ssd_SOURCES = tools/start-stop-daemon.c
+tools_ssd_CPPFLAGS =
 
 # don't bother autoconf'ing these for a simple optional tool
 llvm_version = $(shell echo __clang_major__ | $(CC) -xc -P -E -)
+tools_frr_llvm_cg_CPPFLAGS = $(CPPFLAGS_BASE)
 tools_frr_llvm_cg_CFLAGS = $(AM_CFLAGS) `llvm-config-$(llvm_version) --cflags`
 tools_frr_llvm_cg_LDFLAGS = `llvm-config-$(llvm_version) --ldflags --libs`
 tools_frr_llvm_cg_SOURCES = \