From 13b6c1e150fbc4f51e39c5a8bc76a6b2f72d4243 Mon Sep 17 00:00:00 2001
From: Nashwan Azhari <nazhari@cloudbasesolutions.com>
Date: Mon, 21 Mar 2022 13:56:43 +0200
Subject: [PATCH] Fix max number of samples in experiments on non-64-bit
 systems.

The use of `math.MaxInt64` as the maximum number of samples in the context
of general int variables can lead to inconsistent behavior on non-64-bit
systems.

This patch addresses this using the arbitrary-precision `math/big.Int`
type to store and compare sampling numbers to ensure no
architecture-dependant int size mismatches will occur.

Signed-off-by: Nashwan Azhari <nazhari@cloudbasesolutions.com>
---
 gmeasure/experiment.go | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/gmeasure/experiment.go b/gmeasure/experiment.go
index 2ac521d73..bc8fb7931 100644
--- a/gmeasure/experiment.go
+++ b/gmeasure/experiment.go
@@ -40,6 +40,7 @@ package gmeasure
 import (
 	"fmt"
 	"math"
+	"math/big"
 	"reflect"
 	"sync"
 	"time"
@@ -452,9 +453,11 @@ func (e *Experiment) Sample(callback func(idx int), samplingConfig SamplingConfi
 	if samplingConfig.Duration > 0 {
 		maxTime = time.Now().Add(samplingConfig.Duration)
 	}
-	maxN := math.MaxInt64
+	maxN := big.NewInt(math.MaxInt64)
 	if samplingConfig.N > 0 {
-		maxN = samplingConfig.N
+		// NOTE(aznashwan): we print then parse the samplingConfig.N to future-proof
+		// against variations in the bit size of the standard int type:
+		maxN.SetString(fmt.Sprintf("%d", samplingConfig.N), 10)
 	}
 	numParallel := 1
 	if samplingConfig.NumParallel > numParallel {
@@ -491,7 +494,12 @@ func (e *Experiment) Sample(callback func(idx int), samplingConfig SamplingConfi
 			avgDt = (avgDt*time.Duration(idx-numParallel) + dt) / time.Duration(idx-numParallel+1)
 		}
 		idx += 1
-		if idx >= maxN {
+
+		idxBigInt := big.NewInt(0)
+		// NOTE(aznashwan): we print then parse the integer idx to future-proof
+		// against variations in the bit size of the standard int type:
+		idxBigInt.SetString(fmt.Sprintf("%d", idx), 10)
+		if idxBigInt.Cmp(maxN) >= 0 {
 			return
 		}
 		if time.Now().Add(avgDt).After(maxTime) {