From 21d221eae0ffb0c7d1bd3886c30dc00ae7b24c88 Mon Sep 17 00:00:00 2001
From: slava <kulakov.home@gmail.com>
Date: Tue, 31 Aug 2021 00:06:23 +0300
Subject: [PATCH] Fix data types for CUTime and CSTime stat fields #403 (#404)

* Fix data types for CUTime and CSTime stat fields #403

These two stat fields (CUTime and CSTime) in the /proc/[pid]/stat file should have the signed long data type according to the documentation. But currently in the code their data type is just unsigned int. This commit fixes it and adds more tests.

See for details:
* https://man7.org/linux/man-pages/man5/proc.5.html
* https://man7.org/linux/man-pages/man3/scanf.3.html

Signed-off-by: Vyacheslav Kulakov <kulakov.home@gmail.com>
---
 fixtures.ttar     |  2 +-
 proc_stat.go      |  9 +++++++--
 proc_stat_test.go | 19 +++++++++++++++++--
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/fixtures.ttar b/fixtures.ttar
index 5e7eeef4a..30df09144 100644
--- a/fixtures.ttar
+++ b/fixtures.ttar
@@ -589,7 +589,7 @@ SymlinkTo: /does/not/exist
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Path: fixtures/proc/26232/stat
 Lines: 1
-33 (ata_sff) S 2 0 0 0 -1 69238880 0 0 0 0 0 0 0 0 0 -20 1 0 5 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 1 0 0 0 0 0 0 0 0 0 0 0 0 0
+33 (ata_sff) S 2 0 0 0 -1 69238880 0 0 0 0 0 0 -9223372036854775808 9223372036854775807 0 -20 1 0 5 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 -9223372036854775808 9223372036854775807 0 0 0 0 0 0 0 0 0 0 0 0 0
 Mode: 644
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Path: fixtures/proc/26232/wchan
diff --git a/proc_stat.go b/proc_stat.go
index 8c7b6e80a..ad03d85ef 100644
--- a/proc_stat.go
+++ b/proc_stat.go
@@ -81,10 +81,10 @@ type ProcStat struct {
 	STime uint
 	// Amount of time that this process's waited-for children have been
 	// scheduled in user mode, measured in clock ticks.
-	CUTime uint
+	CUTime int
 	// Amount of time that this process's waited-for children have been
 	// scheduled in kernel mode, measured in clock ticks.
-	CSTime uint
+	CSTime int
 	// For processes running a real-time scheduling policy, this is the negated
 	// scheduling priority, minus one.
 	Priority int
@@ -141,6 +141,11 @@ func (p Proc) Stat() (ProcStat, error) {
 	}
 
 	s.Comm = string(data[l+1 : r])
+
+	// Check the following resources for the details about the particular stat
+	// fields and their data types:
+	// * https://man7.org/linux/man-pages/man5/proc.5.html
+	// * https://man7.org/linux/man-pages/man3/scanf.3.html
 	_, err = fmt.Fscan(
 		bytes.NewBuffer(data[r+2:]),
 		&s.State,
diff --git a/proc_stat_test.go b/proc_stat_test.go
index 53491050e..8be1e1318 100644
--- a/proc_stat_test.go
+++ b/proc_stat_test.go
@@ -14,6 +14,7 @@
 package procfs
 
 import (
+	"math"
 	"os"
 	"testing"
 )
@@ -76,16 +77,30 @@ func TestProcStat(t *testing.T) {
 	}
 }
 
-func TestProcStatIgnored(t *testing.T) {
+func TestProcStatLimits(t *testing.T) {
 	p, err := getProcFixtures(t).Proc(26232)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	_, err = p.Stat()
+	s, err := p.Stat()
 	if err != nil {
 		t.Errorf("want not error, have %s", err)
 	}
+
+	// max values of stat int fields
+	for _, test := range []struct {
+		name string
+		want int
+		have int
+	}{
+		{name: "waited for children user time", want: math.MinInt64, have: s.CUTime},
+		{name: "waited for children system time", want: math.MaxInt64, have: s.CSTime},
+	} {
+		if test.want != test.have {
+			t.Errorf("want %s %d, have %d", test.name, test.want, test.have)
+		}
+	}
 }
 
 func TestProcStatComm(t *testing.T) {