perf tools: Add a simple expression parser for JSON

Add a simple expression parser good enough to parse JSON relation
expressions. The parser is implemented using bison.

This is just intended as an simple parser for internal usage in the
event lists, not the beginning of a "perf scripting language"

v2: Use expr__ prefix instead of expr_
    Support multiple free variables for parser

Committer note:

The v2 patch had:

  %define api.pure full

In expr.y, that is a feature introduced in bison 2.7, to have reentrant
parsers, not using global variables, which would make tools/perf stop
building with the bison version shipped in older distros, so Andi
realised that the other parsers (e.g. parse-events.y) were using:

  %pure-parser

Which is present in older versions of bison and fits the bill.

I added:

  CFLAGS_expr-bison.o += -DYYENABLE_NLS=0 -DYYLTYPE_IS_TRIVIAL=0 -w

To finally make it build, copying what was there for pmu-bison.o,
another parser.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20170320201711.14142-8-andi@firstfloor.org
[ stdlib.h is needed in tests/expr.c for free() fixing build in systems such as ubuntu:16.04-x-s390 ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
new file mode 100644
index 000000000000..6c6a3749aaf6
--- /dev/null
+++ b/tools/perf/tests/expr.c
@@ -0,0 +1,56 @@
+#include "util/debug.h"
+#include "util/expr.h"
+#include "tests.h"
+#include <stdlib.h>
+
+static int test(struct parse_ctx *ctx, const char *e, double val2)
+{
+	double val;
+
+	if (expr__parse(&val, ctx, &e))
+		TEST_ASSERT_VAL("parse test failed", 0);
+	TEST_ASSERT_VAL("unexpected value", val == val2);
+	return 0;
+}
+
+int test__expr(int subtest __maybe_unused)
+{
+	const char *p;
+	const char **other;
+	double val;
+	int ret;
+	struct parse_ctx ctx;
+	int num_other;
+
+	expr__ctx_init(&ctx);
+	expr__add_id(&ctx, "FOO", 1);
+	expr__add_id(&ctx, "BAR", 2);
+
+	ret = test(&ctx, "1+1", 2);
+	ret |= test(&ctx, "FOO+BAR", 3);
+	ret |= test(&ctx, "(BAR/2)%2", 1);
+	ret |= test(&ctx, "1 - -4",  5);
+	ret |= test(&ctx, "(FOO-1)*2 + (BAR/2)%2 - -4",  5);
+
+	if (ret)
+		return ret;
+
+	p = "FOO/0";
+	ret = expr__parse(&val, &ctx, &p);
+	TEST_ASSERT_VAL("division by zero", ret == 1);
+
+	p = "BAR/";
+	ret = expr__parse(&val, &ctx, &p);
+	TEST_ASSERT_VAL("missing operand", ret == 1);
+
+	TEST_ASSERT_VAL("find other",
+			expr__find_other("FOO + BAR + BAZ + BOZO", "FOO", &other, &num_other) == 0);
+	TEST_ASSERT_VAL("find other", num_other == 3);
+	TEST_ASSERT_VAL("find other", !strcmp(other[0], "BAR"));
+	TEST_ASSERT_VAL("find other", !strcmp(other[1], "BAZ"));
+	TEST_ASSERT_VAL("find other", !strcmp(other[2], "BOZO"));
+	TEST_ASSERT_VAL("find other", other[3] == NULL);
+	free((void *)other);
+
+	return 0;
+}