From 857a060fe3a415c1909ad8a342d9ca21019ab2fc Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <dvyukov@google.com>
Date: Fri, 13 Nov 2020 13:49:27 +0100
Subject: pkg/compiler: check for flags with all equal values

There is no point in having flags when values are equal.
This can only mean a typo or other bug. Check for such cases
and fix 3 existing precedents.
---
 pkg/compiler/check.go             | 12 +++++++++++-
 pkg/compiler/testdata/errors2.txt |  6 ++++++
 sys/linux/netfilter.txt           |  4 ++--
 sys/openbsd/vnet.txt              |  2 +-
 4 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/pkg/compiler/check.go b/pkg/compiler/check.go
index 468b6e35e..022581771 100644
--- a/pkg/compiler/check.go
+++ b/pkg/compiler/check.go
@@ -248,7 +248,7 @@ func (comp *compiler) checkTypes() {
 
 func (comp *compiler) checkTypeValues() {
 	for _, decl := range comp.desc.Nodes {
-		switch decl.(type) {
+		switch n := decl.(type) {
 		case *ast.Call, *ast.Struct, *ast.Resource, *ast.TypeDef:
 			comp.foreachType(decl, func(t *ast.Type, desc *typeDesc,
 				args []*ast.Type, base prog.IntTypeCommon) {
@@ -261,6 +261,16 @@ func (comp *compiler) checkTypeValues() {
 					}
 				}
 			})
+		case *ast.IntFlags:
+			allEqual := len(n.Values) >= 2
+			for _, val := range n.Values {
+				if val.Value != n.Values[0].Value {
+					allEqual = false
+				}
+			}
+			if allEqual {
+				comp.error(n.Pos, "all %v values are equal %v", n.Name.Name, n.Values[0].Value)
+			}
 		}
 	}
 }
diff --git a/pkg/compiler/testdata/errors2.txt b/pkg/compiler/testdata/errors2.txt
index c862358cf..111db587f 100644
--- a/pkg/compiler/testdata/errors2.txt
+++ b/pkg/compiler/testdata/errors2.txt
@@ -370,6 +370,12 @@ foo$534(a ptr[in, flags[large_flags, int8]])	### large_flags U16_MAX=0xffff does
 
 large_flags = U8_MAX, U16_MAX
 
+equal_flags_0 = 0, 0, 0, 0		### all equal_flags_0 values are equal 0
+equal_flags_1 = 42, 42, 42, 42		### all equal_flags_1 values are equal 42
+non_equal_flags = 0, 0, 0, 1
+
+equal_flags_call(a flags[equal_flags_0], b flags[equal_flags_1], c flags[non_equal_flags])
+
 type type500 proc[C1, 8, int8]	### values starting from 1 with step 8 overflow base type for 32 procs
 type type501 int8		### unused type type501
 type type502[C] const[C, int8]	### unused type type502
diff --git a/sys/linux/netfilter.txt b/sys/linux/netfilter.txt
index a620f40e7..dc8655ec0 100644
--- a/sys/linux/netfilter.txt
+++ b/sys/linux/netfilter.txt
@@ -573,7 +573,7 @@ xt_ipcomp {
 	hdrres		const[0, int8]
 }
 
-xt_ipcomp_flags = XT_IPCOMP_INV_SPI, XT_IPCOMP_INV_MASK
+xt_ipcomp_flags = XT_IPCOMP_INV_SPI
 
 xt_statistic_info {
 	mode	bool16
@@ -768,7 +768,7 @@ xt_esp {
 	invflags	flags[xt_esp_flags, int8]
 }
 
-xt_esp_flags = XT_ESP_INV_SPI, XT_ESP_INV_MASK
+xt_esp_flags = XT_ESP_INV_SPI
 
 xt_cpu_info {
 	cpu	int32
diff --git a/sys/openbsd/vnet.txt b/sys/openbsd/vnet.txt
index bd18f899c..6c229b969 100644
--- a/sys/openbsd/vnet.txt
+++ b/sys/openbsd/vnet.txt
@@ -566,7 +566,7 @@ ipv6_hopots_ext_header {
 	options		array[ipv6_tlv_option]
 } [packed, align[8]]
 
-ipv6_routing_types = IPV6_RTHDR_LOOSE, IPV6_RTHDR_TYPE_0
+ipv6_routing_types = IPV6_RTHDR_LOOSE
 
 ipv6_rt_hdr {
 	next_header	flags[ipv6_types, int8]
-- 
cgit mrf-deployment