Avoid overflow when MaxConns is set to MaxInt32

fixes #2379

Author: jackc

pgxpool/pool.go

@@ -591,7 +591,7 @@ func (p *Pool) Acquire(ctx context.Context) (c *Conn, err error) {
 	// Try to acquire from the connection pool up to maxConns + 1 times, so that
 	// any that fatal errors would empty the pool and still at least try 1 fresh
 	// connection.
-	for range p.maxConns + 1 {
+	for range int(p.maxConns) + 1 {
 		res, err := p.p.Acquire(ctx)
 		if err != nil {
 			return nil, err

pgxpool/pool_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math"
 	"os"
 	"sync/atomic"
 	"testing"
@@ -245,6 +246,27 @@ func TestPoolAcquireChecksIdleConnsWithShouldPing(t *testing.T) {
 	c.Release()
 }
 
+// https://github.com/jackc/pgx/issues/2379
+func TestPoolAcquireWithMaxConnsEqualsMaxInt32(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+	defer cancel()
+
+	config, err := pgxpool.ParseConfig(os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(t, err)
+
+	config.MaxConns = math.MaxInt32
+
+	pool, err := pgxpool.NewWithConfig(ctx, config)
+	require.NoError(t, err)
+	defer pool.Close()
+
+	c, err := pool.Acquire(ctx)
+	require.NoError(t, err)
+	c.Release()
+}
+
 func TestPoolAcquireFunc(t *testing.T) {
 	t.Parallel()