[LTP] [RFC PATCH v3 2/2] Start libclang based analyzer and TEST() check

[Richard Palethorpe]

This uses the stable Clang C API to find usages of the TEST()
macro.

This Clang API only exposes the AST along with some other utilities
for evaluating constants, indexing, auto completion and source
rewriting. This is somewhat less than what Smatch, Coccinelle and the
unstable Clang C++ APIs expose. However it is a simple, stable and
well supported C API.

For now we are limiting ourselves to the functions available in the
LLVM-10 release.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
 tools/clang-check/main.c | 238 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 238 insertions(+)
 create mode 100644 tools/clang-check/main.c

diff --git a/tools/clang-check/main.c b/tools/clang-check/main.c
new file mode 100644
index 000000000..feb6774fd
--- /dev/null
+++ b/tools/clang-check/main.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021 SUSE LLC <rpalethorpe@suse.com>
+ * Copyright (c) 2017 Petr Vorel <pvorel@suse.cz>
+ *
+ * Entry point for the LTP static analyser.
+ *
+ * Scans the AST (Abstract Syntax Tree) generated by Clang. We look at
+ * the kind of each node and decide if one or more checks can be run
+ * on it. If at least the kind of node matches we pass it to the
+ * checking function. This function may then perform further
+ * matching. Finally, if it finds the sub tree is the type of thing
+ * which needs to be checked, then it performs the check and emits an
+ * error if it fails.
+ *
+ * AST Nodes are called CXCursor by libclang. We use the library's
+ * visitor functions to recurse into the AST.
+ *
+ * This program takes the same arguments the Clang compiler
+ * frontend does. Although some are ignored by libclang.
+ */
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "../../include/config.h"
+
+#define attr_unused __attribute__((unused))
+
+#if HAVE_CLANG_C_INDEX_H
+
+#include <clang-c/Index.h>
+
+/* The rules for test, library and tool code are different */
+enum ltp_tu_kind {
+	LTP_LIB,
+	LTP_OTHER,
+};
+
+/* Holds information about the TU which we gathered on the first pass */
+static struct {
+	enum ltp_tu_kind tu_kind;
+} tu_info;
+
+static const char *const ansi_red = "\033[1;31m";
+static const char *const ansi_reset = "\033[0m";
+static const char *const ansi_bold = "\033[1m";
+
+static unsigned error_flag;
+
+/* Copied from lib/tst_ansi_color.c */
+static int color_enabled(const int fd)
+{
+	static int color;
+
+	if (color)
+		return color - 1;
+
+	const char *const env = getenv("LTP_COLORIZE_OUTPUT");
+
+	if (env) {
+		if (!strcmp(env, "n") || !strcmp(env, "0"))
+			color = 1;
+
+		if (!strcmp(env, "y") || !strcmp(env, "1"))
+			color = 2;
+
+		return color - 1;
+	}
+
+	if (isatty(fd) == 0)
+		color = 1;
+	else
+		color = 2;
+
+	return color - 1;
+}
+
+static void emit_error(const char *const error_msg)
+{
+	if (color_enabled(STDERR_FILENO)) {
+		dprintf(STDERR_FILENO,
+			"%sERROR%s: %s%s%s\n",
+			ansi_red, ansi_reset,
+			ansi_bold, error_msg, ansi_reset);
+	} else {
+		dprintf(STDERR_FILENO, "ERROR: %s\n", error_msg);
+	}
+}
+
+static void emit_check_error(CXCursor offending_cursor, const char *const error_msg)
+{
+	CXSourceLocation loc = clang_getCursorLocation(offending_cursor);
+	CXFile loc_file;
+	unsigned loc_line, loc_column;
+	CXString file_name;
+
+	error_flag = 1;
+
+	clang_getFileLocation(loc, &loc_file, &loc_line, &loc_column,
+			      /*offset=*/NULL);
+	file_name = clang_getFileName(loc_file);
+
+	if (color_enabled(STDERR_FILENO)) {
+		dprintf(STDERR_FILENO,
+			"%s:%u:%u: %sCHECK ERROR%s: %s%s%s\n",
+			clang_getCString(file_name), loc_line, loc_column,
+			ansi_red, ansi_reset,
+			ansi_bold, error_msg, ansi_reset);
+	} else {
+		dprintf(STDERR_FILENO,
+			"%s:%u:%u: CHECK ERROR: %s\n",
+			clang_getCString(file_name), loc_line, loc_column,
+			error_msg);
+	}
+
+	clang_disposeString(file_name);
+}
+
+static int cursor_cmp_spelling(const char *const spelling, CXCursor cursor)
+{
+	CXString cursor_spelling = clang_getCursorSpelling(cursor);
+	const int ret = strcmp(spelling, clang_getCString(cursor_spelling));
+
+	clang_disposeString(cursor_spelling);
+
+	return ret;
+}
+
+static int cursor_type_cmp_spelling(const char *const spelling, CXCursor cursor)
+{
+	CXType ctype = clang_getCursorType(cursor);
+	CXString ctype_spelling = clang_getTypeSpelling(ctype);
+	const int ret = strcmp(spelling, clang_getCString(ctype_spelling));
+
+	clang_disposeString(ctype_spelling);
+
+	return ret;
+}
+
+/*
+ * Check if the TEST() macro is used inside the library.
+ *
+ * This check takes an AST node which should already be known to be a
+ * macro expansion kind.
+ *
+ * If the TU appears to be a test executable then the test does not
+ * apply. So in that case we return.
+ *
+ * If the macro expansion AST node is spelled TEST, then we emit an
+ * error. Otherwise do nothing.
+ */
+static void check_TEST_macro(CXCursor macro_cursor)
+{
+	if (tu_info.tu_kind != LTP_LIB)
+		return;
+
+	if (!cursor_cmp_spelling("TEST", macro_cursor)) {
+		emit_check_error(macro_cursor,
+			   "TEST() macro should not be used in library");
+	}
+}
+
+/* Recursively visit each AST node and run checks based on node kind */
+static enum CXChildVisitResult check_visitor(CXCursor cursor,
+					     attr_unused CXCursor parent,
+					     attr_unused CXClientData client_data)
+{
+	CXSourceLocation loc = clang_getCursorLocation(cursor);
+
+	if (clang_Location_isInSystemHeader(loc))
+		return CXChildVisit_Continue;
+
+	switch (clang_getCursorKind(cursor)) {
+	case CXCursor_MacroExpansion:
+			check_TEST_macro(cursor);
+		break;
+	default:
+		break;
+	}
+
+	return CXChildVisit_Recurse;
+}
+
+static void collect_info_from_args(const int argc, const char *const *const argv)
+{
+	int i;
+
+	for (i = 0; i < argc; i++) {
+		if (!strcmp("-DLTPLIB", argv[i])) {
+			tu_info.tu_kind = LTP_LIB;
+		}
+	}
+}
+
+int main(const int argc, const char *const *const argv)
+{
+	CXIndex cindex = clang_createIndex(0, 1);
+	CXTranslationUnit tu;
+	CXCursor tuc;
+	enum CXErrorCode ret;
+
+	tu_info.tu_kind = LTP_OTHER;
+	collect_info_from_args(argc, argv);
+
+	ret = clang_parseTranslationUnit2(
+		cindex,
+		/*source_filename=*/NULL,
+		argv + 1, argc - 1,
+		/*unsaved_files=*/NULL, /*num_unsaved_files=*/0,
+		CXTranslationUnit_DetailedPreprocessingRecord,
+		&tu);
+
+	if (ret != CXError_Success) {
+		emit_error("Failed to parse translation unit!");
+		return 1;
+	}
+
+	tuc = clang_getTranslationUnitCursor(tu);
+
+	clang_visitChildren(tuc, check_visitor, NULL);
+
+	/* Stop leak sanitizer from complaining */
+	clang_disposeTranslationUnit(tu);
+	clang_disposeIndex(cindex);
+
+	return error_flag;
+}
+
+#else
+
+int main(const attr_unused int argc, const attr_unused char *const *const argv)
+{
+	emit_error("clang-checks was not built correctly; libclang headers are not installed!\n");
+	return 1;
+}
+
+#endif
-- 
2.31.1