[PATCH 12/12] Add check_all_func_returns

Add a new check type that looks for unchecked returns on *all* functions,
mimicking the old behaviour of lint. A cast to (void) silences the warning.

Signed-off-by: John Levon <[email protected]>
---
 check_all_func_returns.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++
 check_list.h             |  3 +++
 2 files changed, 69 insertions(+)
 create mode 100644 check_all_func_returns.c

diff --git a/check_all_func_returns.c b/check_all_func_returns.c
new file mode 100644
index 0000000..f4ba58d
--- /dev/null
+++ b/check_all_func_returns.c
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2018 Joyent, 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; if not, see http://www.gnu.org/copyleft/gpl.txt
+ */
+
+/*
+ * Like lint of old, check that every return value from every function is used.
+ * Casting to (void) will silence this check.
+ */
+
+#include "smatch.h"
+#include "smatch_slist.h"
+
+static void check_func_return(struct expression *expr)
+{
+	struct symbol *sym = get_real_base_type(get_type(expr->fn));
+	const char *func = expr_to_str(expr->fn);
+	struct statement *stmt;
+
+	if (sym == NULL) {
+		sm_error("unknown type for func '%s'", func);
+		return;
+	}
+
+	/*
+	 * There is never any need to check these returns.
+	 */
+	if (strcmp(func, "memcpy") == 0 ||
+	    strcmp(func, "memmove") == 0 ||
+	    strcmp(func, "memset") == 0)
+		return;
+
+	/*
+	 * Either we got the return type already (direct call),
+	 * or we need to go one further (function pointer call)
+	 */
+	if (sym == &void_ctype || (sym->type == SYM_FN &&
+		get_real_base_type(sym) == &void_ctype))
+		return;
+
+	stmt = last_ptr_list((struct ptr_list *)big_statement_stack);
+
+	if (stmt->type == STMT_EXPRESSION && stmt->expression == expr)
+		sm_error("unchecked function return '%s'", expr_to_str(expr->fn));
+}
+
+void check_all_func_returns(int id)
+{
+	if (option_project != PROJ_ILLUMOS_KERNEL &&
+	    option_project != PROJ_ILLUMOS_USER)
+		return;
+
+	add_hook(&check_func_return, FUNCTION_CALL_HOOK);
+}
diff --git a/check_list.h b/check_list.h
index 055e630..cbe783d 100644
--- a/check_list.h
+++ b/check_list.h
@@ -192,6 +192,9 @@ CK(check_implicit_dependencies)
 CK(check_wine_filehandles)
 CK(check_wine_WtoA)
 
+/* illumos specific stuff */
+CK(check_all_func_returns)
+
 #include "check_list_local.h"
 
 CK(register_scope)
-- 
1.8.3.1