pkg/declextract: move const handling logic from the clang tool

Export raw info about consts from the clang tool, and let the Go part handle it.
The less logic is in the clang tool, the better. Also this will allow to remove
unused includes when we know which consts we ended up using.
The more includes we include, the higher the chances we include something
that's broken.

3 files changed, 52 insertions, 25 deletions

diff --git a/pkg/declextract/declextract.go b/pkg/declextract/declextract.go
index 1f4592523..fdf06b373 100644
--- a/pkg/declextract/declextract.go
+++ b/pkg/declextract/declextract.go
@@ -29,7 +29,7 @@ func Run(out *Output, probe *ifaceprobe.Info, syscallRename map[string][]string,
 	}
 	ctx.processFunctions()
 	ctx.processTypingFacts()
-	ctx.processIncludes()
+	ctx.processConsts()
 	ctx.processEnums()
 	ctx.processStructs()
 	ctx.processSyscalls()
@@ -47,6 +47,8 @@ type context struct {
 	structs       map[string]*Struct
 	funcs         map[string]*Function
 	facts         map[string]*typingNode
+	includes      []string
+	defines       []define
 	uniqualizer   map[string]int
 	interfaces    []*Interface
 	descriptions  *bytes.Buffer
@@ -54,6 +56,11 @@ type context struct {
 	errs          []error
 }
 
+type define struct {
+	Name  string
+	Value string
+}
+
 func (ctx *context) error(msg string, args ...any) {
 	ctx.errs = append(ctx.errs, fmt.Errorf(msg, args...))
 }
@@ -68,14 +75,7 @@ func (ctx *context) trace(msg string, args ...any) {
 	}
 }
 
-func (ctx *context) processIncludes() {
-	// These additional includes must be at the top, because other kernel headers
-	// are broken and won't compile without these additional ones included first.
-	ctx.Includes = append([]string{
-		"vdso/bits.h",
-		"linux/types.h",
-		"net/netlink.h",
-	}, ctx.Includes...)
+func (ctx *context) processConsts() {
 	replaces := map[string]string{
 		// Arches may use some includes from asm-generic and some from arch/arm.
 		// If the arch used for extract used asm-generic for a header,
@@ -84,11 +84,40 @@ func (ctx *context) processIncludes() {
 		"include/uapi/asm-generic/ioctls.h":  "asm/ioctls.h",
 		"include/uapi/asm-generic/sockios.h": "asm/sockios.h",
 	}
-	for i, inc := range ctx.Includes {
-		if replace := replaces[inc]; replace != "" {
-			ctx.Includes[i] = replace
+	defineDedup := make(map[string]bool)
+	for _, ci := range ctx.Consts {
+		if strings.Contains(ci.Filename, "/uapi/") && !strings.Contains(ci.Filename, "arch/x86/") &&
+			strings.HasSuffix(ci.Filename, ".h") {
+			filename := ci.Filename
+			if replace := replaces[filename]; replace != "" {
+				filename = replace
+			}
+			ctx.includes = append(ctx.includes, filename)
+			continue
 		}
+		// Remove duplicate defines (even with different values). Unfortunately we get few of these.
+		// There are some syscall numbers (presumably for 32/64 bits), and some macros that
+		// are defined in different files to different values (e.g. WMI_DATA_BE_SVC).
+		// Ideally we somehow rename defines (chosing one random value is never correct).
+		// But for now this helps to prevent compilation errors.
+		if defineDedup[ci.Name] {
+			continue
+		}
+		defineDedup[ci.Name] = true
+		ctx.defines = append(ctx.defines, define{
+			Name:  ci.Name,
+			Value: fmt.Sprint(ci.Value),
+		})
 	}
+	ctx.includes = sortAndDedupSlice(ctx.includes)
+	ctx.defines = sortAndDedupSlice(ctx.defines)
+	// These additional includes must be at the top, because other kernel headers
+	// are broken and won't compile without these additional ones included first.
+	ctx.includes = append([]string{
+		"vdso/bits.h",
+		"linux/types.h",
+		"net/netlink.h",
+	}, ctx.includes...)
 }
 
 func (ctx *context) processEnums() {
diff --git a/pkg/declextract/entity.go b/pkg/declextract/entity.go
index 266647ed8..8167d8b99 100644
--- a/pkg/declextract/entity.go
+++ b/pkg/declextract/entity.go
@@ -12,8 +12,7 @@ import (
 
 type Output struct {
 	Functions       []*Function      `json:"functions,omitempty"`
-	Includes        []string         `json:"includes,omitempty"`
-	Defines         []*Define        `json:"defines,omitempty"`
+	Consts          []*ConstInfo     `json:"consts,omitempty"`
 	Enums           []*Enum          `json:"enums,omitempty"`
 	Structs         []*Struct        `json:"structs,omitempty"`
 	Syscalls        []*Syscall       `json:"syscalls,omitempty"`
@@ -36,9 +35,10 @@ type Function struct {
 	facts   map[string]*typingNode
 }
 
-type Define struct {
-	Name  string `json:"name,omitempty"`
-	Value string `json:"value,omitempty"`
+type ConstInfo struct {
+	Name     string `json:"name"`
+	Filename string `json:"filename"`
+	Value    int64  `json:"value"`
 }
 
 type Field struct {
@@ -199,8 +199,7 @@ type EntityGlobalAddr struct {
 
 func (out *Output) Merge(other *Output) {
 	out.Functions = append(out.Functions, other.Functions...)
-	out.Includes = append(out.Includes, other.Includes...)
-	out.Defines = append(out.Defines, other.Defines...)
+	out.Consts = append(out.Consts, other.Consts...)
 	out.Enums = append(out.Enums, other.Enums...)
 	out.Structs = append(out.Structs, other.Structs...)
 	out.Syscalls = append(out.Syscalls, other.Syscalls...)
@@ -212,8 +211,7 @@ func (out *Output) Merge(other *Output) {
 
 func (out *Output) SortAndDedup() {
 	out.Functions = sortAndDedupSlice(out.Functions)
-	out.Includes = sortAndDedupSlice(out.Includes)
-	out.Defines = sortAndDedupSlice(out.Defines)
+	out.Consts = sortAndDedupSlice(out.Consts)
 	out.Enums = sortAndDedupSlice(out.Enums)
 	out.Structs = sortAndDedupSlice(out.Structs)
 	out.Syscalls = sortAndDedupSlice(out.Syscalls)
@@ -229,8 +227,8 @@ func (out *Output) SetSourceFile(file string, updatePath func(string) string) {
 	for _, fn := range out.Functions {
 		fn.File = updatePath(fn.File)
 	}
-	for i, inc := range out.Includes {
-		out.Includes[i] = updatePath(inc)
+	for _, ci := range out.Consts {
+		ci.Filename = updatePath(ci.Filename)
 	}
 	for _, call := range out.Syscalls {
 		call.SourceFile = file
diff --git a/pkg/declextract/serialization.go b/pkg/declextract/serialization.go
index d69358679..571336097 100644
--- a/pkg/declextract/serialization.go
+++ b/pkg/declextract/serialization.go
@@ -39,14 +39,14 @@ func (ctx *context) fmt(msg string, args ...any) {
 }
 
 func (ctx *context) serializeIncludes() {
-	for _, inc := range ctx.Includes {
+	for _, inc := range ctx.includes {
 		ctx.fmt("include <%s>\n", inc)
 	}
 	ctx.fmt("\n")
 }
 
 func (ctx *context) serializeDefines() {
-	for _, def := range ctx.Defines {
+	for _, def := range ctx.defines {
 		ctx.fmt("define %v %v\n", def.Name, def.Value)
 	}
 	ctx.fmt("\n")