Fix crash with -Wall on new GCC

build_function_call() passes improper arguments to some further function,
leading to a crash when -Wall is enabled.
I sent a question about it to the GCC mailing lists, can read further
here: https://gcc.gnu.org/pipermail/gcc/2020-April/232127.html

Makefile

@@ -8,7 +8,7 @@ $(PLUGIN): plugin.c
 	$(GXX) -g -Wall -Werror -I`$(GCC) -print-file-name=plugin`/include -fpic -shared -o $@ $<
 
 plugin_test.o: plugin_test.c $(PLUGIN)
-	$(GCC) -O2 -fplugin=./$(PLUGIN) plugin_test.c -c
+	$(GCC) -Wall -Werror -O2 -fplugin=./$(PLUGIN) plugin_test.c -c
 
 tester: tester.c plugin_test.o
 	$(GCC) $^ -o $@

plugin.c

@@ -43,6 +43,29 @@ static tree printf_decl = NULL_TREE;
 static tree abort_decl = NULL_TREE;
 static tree sprintf_decl = NULL_TREE;
 
+// based on build_function_call(), with some fixes.
+// see https://gcc.gnu.org/pipermail/gcc/2020-April/232127.html for explanation.
+tree my_build_function_call(location_t loc, tree function, tree params)
+{
+    const int len = list_length(params);
+
+    vec<tree, va_gc> *v;
+    auto_vec<location_t> argloc(len);
+    tree ret;
+
+    vec_alloc(v, len);
+    for (; params; params = TREE_CHAIN(params)) {
+        tree param = TREE_VALUE(params);
+        v->quick_push(param);
+        argloc.quick_push(EXPR_HAS_LOCATION(param) ? EXPR_LOCATION(param) : loc);
+    }
+
+    ret = c_build_function_call_vec(loc, argloc, function, v, NULL);
+    vec_free(v);
+
+    return ret;
+}
+
 // heuristic to check if cond_expr is the expression generated by glibc's "assert" macro, which is:
 // ((void) sizeof ((EXPR) ? 1 : 0), __extension__ ({ if (EXPR) ; else __assert_fail ("EXPR", "file.c", line, __extension__ __PRETTY_FUNCTION__); }))
 // the generated cond_expr has COND_EXPR_COND as the assert's condition,
@@ -153,12 +176,12 @@ static void make_assert_expr_printf(location_t here, tree call__assert_fail, tre
         TREE_STRING_POINTER(file_arg), TREE_INT_CST_LOW(line_arg));
 
     tree header_line = build_string_literal(strlen(buf) + 1, buf);
-    append_to_statement_list(build_function_call(here, printf_decl,
+    append_to_statement_list(my_build_function_call(here, printf_decl,
         tree_cons(NULL_TREE, header_line,
         tree_cons(NULL_TREE, function_arg, NULL_TREE))), stmts);
 
     tree format_str = build_string_literal_from_literal("> assert(%s)\n");
-    append_to_statement_list(build_function_call(here, printf_decl,
+    append_to_statement_list(my_build_function_call(here, printf_decl,
         tree_cons(NULL_TREE, format_str,
         // can just use the original argument directly in our call..
         tree_cons(NULL_TREE, CALL_EXPR_ARG(call__assert_fail, 0), NULL_TREE))), stmts);
@@ -326,7 +349,7 @@ static void make_decl_subexpressions_repr(location_t here, struct expr_list *lis
         (void)snprintf(buf, sizeof(buf), "  %s = %s\n", get_format_for_expr(expr),
             IDENTIFIER_POINTER(DECL_NAME(raw_expr)));
 
-        tree printf_call = build_function_call(here, printf_decl,
+        tree printf_call = my_build_function_call(here, printf_decl,
             tree_cons(NULL_TREE, build_string_literal(strlen(buf) + 1, buf),
             tree_cons(NULL_TREE, expr, NULL_TREE)));
 
@@ -344,7 +367,7 @@ static tree make_buf_ref_addr(location_t here, tree buf_param, tree buf_pos) {
 
 // creats a `buf_pos += sprintf(...)` with given arguments.
 static tree make_repr_sprintf(location_t here, tree buf_param, tree buf_pos, const char *format, tree args) {
-    tree sprintf_call = build_function_call(here, sprintf_decl,
+    tree sprintf_call = my_build_function_call(here, sprintf_decl,
             tree_cons(NULL_TREE, make_buf_ref_addr(here, buf_param, buf_pos),
             tree_cons(NULL_TREE, build_string_literal(strlen(format) + 1, format), args)));
 
@@ -565,26 +588,26 @@ static tree make_assert_failed_body(location_t here, tree cond_expr) {
     append_to_statement_list(make_conditional_expr_repr(&params, COND_EXPR_COND(cond_expr)), &stmts);
 
     // print the repr buf now
-    tree printf_call = build_function_call(here, printf_decl,
+    tree printf_call = my_build_function_call(here, printf_decl,
         tree_cons(NULL_TREE, build_string_literal_from_literal("  assert(%s)\n"),
         tree_cons(NULL_TREE, buf_param, NULL_TREE)));
     append_to_statement_list(printf_call, &stmts);
 
-    append_to_statement_list(build_function_call(here, printf_decl,
+    append_to_statement_list(my_build_function_call(here, printf_decl,
         tree_cons(NULL_TREE, build_string_literal_from_literal("> subexpressions:\n"), NULL_TREE)),
         &stmts);
 
     // add DECLs subexpressions repr
     make_decl_subexpressions_repr(here, &repr_exprs, &stmts);
 
     // print call buf repr
-    printf_call = build_function_call(here, printf_decl,
+    printf_call = my_build_function_call(here, printf_decl,
         tree_cons(NULL_TREE, build_string_literal_from_literal("%s"),
         tree_cons(NULL_TREE, call_buf_param, NULL_TREE)));
     append_to_statement_list(printf_call, &stmts);
 
     // finally, an abort call
-    tree abort_call = build_function_call(here, abort_decl, NULL_TREE);
+    tree abort_call = my_build_function_call(here, abort_decl, NULL_TREE);
     append_to_statement_list(abort_call, &stmts);
 
     return c_build_bind_expr(here, block, stmts);

tests/test_assert_rewrite.py

@@ -23,9 +23,6 @@ def run_tester(test_prototype, test_code, calling_code, *, extra_test="",
         test.write(HEADERS + extra_test + "{0} {{ {1} }}".format(test_prototype, test_code))
         test.flush()
         extra_opts = ["-Werror", "-Wall", ]
-        if b"9.1.0" in subprocess.check_output([GCC, "--version"]):
-            # TODO -Werror kills GCC 9.1.0 if the plugin is active
-            extra_opts = []
         subprocess.check_call([GCC,
                                "-fplugin={}".format(ASSERT_INTROSPECT_SO),
                                "-c", test.name, "-o", obj.name] + extra_opts)