runtime: move atoi to internal/runtime/strconv

Moving to a smaller package allows its use in other internal/runtime
packages.

This isn't internal/strconvlite since it can't be used directly by
strconv.

For #73193.

Change-Id: I6a6a636c9c8b3f06b5fd6c07fe9dd5a7a37d1429
Reviewed-on: https://go-review.googlesource.com/c/go/+/672697
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

14 files changed, 208 insertions, 180 deletions

diff --git a/src/cmd/internal/objabi/pkgspecial.go b/src/cmd/internal/objabi/pkgspecial.go
index 55b66b6055..d4773b1ecf 100644
--- a/src/cmd/internal/objabi/pkgspecial.go
+++ b/src/cmd/internal/objabi/pkgspecial.go
@@ -53,6 +53,7 @@ var runtimePkgs = []string{
 	"internal/runtime/gc",
 	"internal/runtime/maps",
 	"internal/runtime/math",
+	"internal/runtime/strconv",
 	"internal/runtime/sys",
 	"internal/runtime/syscall",
 
diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index b261af47e2..4f366b34a1 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -97,6 +97,7 @@ var depsRules = `
 	< internal/runtime/gc
 	< internal/runtime/math
 	< internal/runtime/maps
+	< internal/runtime/strconv
 	< runtime
 	< sync/atomic
 	< internal/sync
diff --git a/src/internal/runtime/math/math.go b/src/internal/runtime/math/math.go
index e0fdc3438d..7b616cff79 100644
--- a/src/internal/runtime/math/math.go
+++ b/src/internal/runtime/math/math.go
@@ -8,7 +8,10 @@ import "internal/goarch"
 
 const (
 	MaxUint32  = ^uint32(0)
+	MaxUint64  = ^uint64(0)
 	MaxUintptr = ^uintptr(0)
+
+	MaxInt64 = int64(MaxUint64 >> 1)
 )
 
 // MulUintptr returns a * b and whether the multiplication overflowed.
diff --git a/src/internal/runtime/strconv/atoi.go b/src/internal/runtime/strconv/atoi.go
new file mode 100644
index 0000000000..87b3faf6d5
--- /dev/null
+++ b/src/internal/runtime/strconv/atoi.go
@@ -0,0 +1,76 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+import (
+	"internal/runtime/math"
+)
+
+// Atoi64 parses an int64 from a string s.
+// The bool result reports whether s is a number
+// representable by a value of type int64.
+func Atoi64(s string) (int64, bool) {
+	if s == "" {
+		return 0, false
+	}
+
+	neg := false
+	if s[0] == '-' {
+		neg = true
+		s = s[1:]
+	}
+
+	un := uint64(0)
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			return 0, false
+		}
+		if un > math.MaxUint64/10 {
+			// overflow
+			return 0, false
+		}
+		un *= 10
+		un1 := un + uint64(c) - '0'
+		if un1 < un {
+			// overflow
+			return 0, false
+		}
+		un = un1
+	}
+
+	if !neg && un > uint64(math.MaxInt64) {
+		return 0, false
+	}
+	if neg && un > uint64(math.MaxInt64)+1 {
+		return 0, false
+	}
+
+	n := int64(un)
+	if neg {
+		n = -n
+	}
+
+	return n, true
+}
+
+// Atoi is like Atoi64 but for integers
+// that fit into an int.
+func Atoi(s string) (int, bool) {
+	if n, ok := Atoi64(s); n == int64(int(n)) {
+		return int(n), ok
+	}
+	return 0, false
+}
+
+// Atoi32 is like Atoi but for integers
+// that fit into an int32.
+func Atoi32(s string) (int32, bool) {
+	if n, ok := Atoi64(s); n == int64(int32(n)) {
+		return int32(n), ok
+	}
+	return 0, false
+}
+
diff --git a/src/internal/runtime/strconv/atoi_test.go b/src/internal/runtime/strconv/atoi_test.go
new file mode 100644
index 0000000000..49cd6f160a
--- /dev/null
+++ b/src/internal/runtime/strconv/atoi_test.go
@@ -0,0 +1,105 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import (
+	"internal/runtime/strconv"
+	"testing"
+)
+
+const intSize = 32 << (^uint(0) >> 63)
+
+type atoi64Test struct {
+	in  string
+	out int64
+	ok  bool
+}
+
+var atoi64tests = []atoi64Test{
+	{"", 0, false},
+	{"0", 0, true},
+	{"-0", 0, true},
+	{"1", 1, true},
+	{"-1", -1, true},
+	{"12345", 12345, true},
+	{"-12345", -12345, true},
+	{"012345", 12345, true},
+	{"-012345", -12345, true},
+	{"12345x", 0, false},
+	{"-12345x", 0, false},
+	{"98765432100", 98765432100, true},
+	{"-98765432100", -98765432100, true},
+	{"20496382327982653440", 0, false},
+	{"-20496382327982653440", 0, false},
+	{"9223372036854775807", 1<<63 - 1, true},
+	{"-9223372036854775807", -(1<<63 - 1), true},
+	{"9223372036854775808", 0, false},
+	{"-9223372036854775808", -1 << 63, true},
+	{"9223372036854775809", 0, false},
+	{"-9223372036854775809", 0, false},
+}
+
+func TestAtoi(t *testing.T) {
+	switch intSize {
+	case 32:
+		for i := range atoi32tests {
+			test := &atoi32tests[i]
+			out, ok := strconv.Atoi(test.in)
+			if test.out != int32(out) || test.ok != ok {
+				t.Errorf("Atoi(%q) = (%v, %v) want (%v, %v)",
+					test.in, out, ok, test.out, test.ok)
+			}
+		}
+	case 64:
+		for i := range atoi64tests {
+			test := &atoi64tests[i]
+			out, ok := strconv.Atoi(test.in)
+			if test.out != int64(out) || test.ok != ok {
+				t.Errorf("Atoi(%q) = (%v, %v) want (%v, %v)",
+					test.in, out, ok, test.out, test.ok)
+			}
+		}
+	}
+}
+
+type atoi32Test struct {
+	in  string
+	out int32
+	ok  bool
+}
+
+var atoi32tests = []atoi32Test{
+	{"", 0, false},
+	{"0", 0, true},
+	{"-0", 0, true},
+	{"1", 1, true},
+	{"-1", -1, true},
+	{"12345", 12345, true},
+	{"-12345", -12345, true},
+	{"012345", 12345, true},
+	{"-012345", -12345, true},
+	{"12345x", 0, false},
+	{"-12345x", 0, false},
+	{"987654321", 987654321, true},
+	{"-987654321", -987654321, true},
+	{"2147483647", 1<<31 - 1, true},
+	{"-2147483647", -(1<<31 - 1), true},
+	{"2147483648", 0, false},
+	{"-2147483648", -1 << 31, true},
+	{"2147483649", 0, false},
+	{"-2147483649", 0, false},
+}
+
+func TestAtoi32(t *testing.T) {
+	for i := range atoi32tests {
+		test := &atoi32tests[i]
+		out, ok := strconv.Atoi32(test.in)
+		if test.out != out || test.ok != ok {
+			t.Errorf("Atoi32(%q) = (%v, %v) want (%v, %v)",
+				test.in, out, ok, test.out, test.ok)
+		}
+	}
+}
+
diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index e7f5d426e4..a9cc767e30 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -35,8 +35,6 @@ var ReadRandomFailed = &readRandomFailed
 
 var Fastlog2 = fastlog2
 
-var Atoi = atoi
-var Atoi32 = atoi32
 var ParseByteCount = parseByteCount
 
 var Nanotime = nanotime
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index ffaf92debc..ccdebb26fb 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -630,7 +630,7 @@ func mallocinit() {
 	}
 	// Initialize the memory limit here because the allocator is going to look at it
 	// but we haven't called gcinit yet and we're definitely going to allocate memory before then.
-	gcController.memoryLimit.Store(maxInt64)
+	gcController.memoryLimit.Store(math.MaxInt64)
 }
 
 // sysAlloc allocates heap arena space for at least n bytes. The
@@ -1816,7 +1816,7 @@ func profilealloc(mp *m, x unsafe.Pointer, size uintptr) {
 func nextSample() int64 {
 	if MemProfileRate == 0 {
 		// Basically never sample.
-		return maxInt64
+		return math.MaxInt64
 	}
 	if MemProfileRate == 1 {
 		// Sample immediately.
diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index 2e05244d95..044792d6bd 100644
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -8,6 +8,8 @@ import (
 	"internal/cpu"
 	"internal/goexperiment"
 	"internal/runtime/atomic"
+	"internal/runtime/math"
+	"internal/runtime/strconv"
 	_ "unsafe" // for go:linkname
 )
 
@@ -1311,7 +1313,7 @@ func readGOGC() int32 {
 	if p == "off" {
 		return -1
 	}
-	if n, ok := atoi32(p); ok {
+	if n, ok := strconv.Atoi32(p); ok {
 		return n
 	}
 	return 100
@@ -1355,7 +1357,7 @@ func setMemoryLimit(in int64) (out int64) {
 func readGOMEMLIMIT() int64 {
 	p := gogetenv("GOMEMLIMIT")
 	if p == "" || p == "off" {
-		return maxInt64
+		return math.MaxInt64
 	}
 	n, ok := parseByteCount(p)
 	if !ok {
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 5a27ab5e78..c5e55f583e 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -1324,7 +1324,7 @@ HaveSpan:
 		// that we expect to page in.
 		inuse := gcController.mappedReady.Load()
 		// Be careful about overflow, especially with uintptrs. Even on 32-bit platforms
-		// someone can set a really big memory limit that isn't maxInt64.
+		// someone can set a really big memory limit that isn't math.MaxInt64.
 		if uint64(scav)+inuse > uint64(limit) {
 			bytesToScavenge = uintptr(uint64(scav) + inuse - uint64(limit))
 			forceScavenge = true
diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index f24d18027b..3071e32202 100644
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -8,6 +8,7 @@ import (
 	"internal/abi"
 	"internal/goarch"
 	"internal/runtime/atomic"
+	"internal/runtime/strconv"
 	"internal/runtime/syscall"
 	"unsafe"
 )
@@ -341,7 +342,7 @@ func getHugePageSize() uintptr {
 		return 0
 	}
 	n-- // remove trailing newline
-	v, ok := atoi(slicebytetostringtmp((*byte)(ptr), int(n)))
+	v, ok := strconv.Atoi(slicebytetostringtmp((*byte)(ptr), int(n)))
 	if !ok || v < 0 {
 		v = 0
 	}
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 1ca800c5fd..5d3e4e4953 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -11,6 +11,7 @@ import (
 	"internal/goos"
 	"internal/runtime/atomic"
 	"internal/runtime/exithook"
+	"internal/runtime/strconv"
 	"internal/runtime/sys"
 	"internal/stringslite"
 	"unsafe"
@@ -900,7 +901,7 @@ func schedinit() {
 	lock(&sched.lock)
 	sched.lastpoll.Store(nanotime())
 	procs := ncpu
-	if n, ok := atoi32(gogetenv("GOMAXPROCS")); ok && n > 0 {
+	if n, ok := strconv.Atoi32(gogetenv("GOMAXPROCS")); ok && n > 0 {
 		procs = n
 	}
 	if procresize(procs) != nil {
diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go
index 2132ceecb2..5beaa4dd74 100644
--- a/src/runtime/runtime1.go
+++ b/src/runtime/runtime1.go
@@ -8,6 +8,7 @@ import (
 	"internal/bytealg"
 	"internal/goarch"
 	"internal/runtime/atomic"
+	"internal/runtime/strconv"
 	"unsafe"
 )
 
@@ -526,13 +527,13 @@ func parsegodebug(godebug string, seen map[string]bool) {
 		// is int, not int32, and should only be updated
 		// if specified in GODEBUG.
 		if seen == nil && key == "memprofilerate" {
-			if n, ok := atoi(value); ok {
+			if n, ok := strconv.Atoi(value); ok {
 				MemProfileRate = n
 			}
 		} else {
 			for _, v := range dbgvars {
 				if v.name == key {
-					if n, ok := atoi32(value); ok {
+					if n, ok := strconv.Atoi32(value); ok {
 						if seen == nil && v.value != nil {
 							*v.value = n
 						} else if v.atomic != nil {
@@ -572,7 +573,7 @@ func setTraceback(level string) {
 		fallthrough
 	default:
 		t = tracebackAll
-		if n, ok := atoi(level); ok && n == int(uint32(n)) {
+		if n, ok := strconv.Atoi(level); ok && n == int(uint32(n)) {
 			t |= uint32(n) << tracebackShift
 		}
 	}
diff --git a/src/runtime/string.go b/src/runtime/string.go
index 7bb9d58de0..44d586bc53 100644
--- a/src/runtime/string.go
+++ b/src/runtime/string.go
@@ -8,6 +8,8 @@ import (
 	"internal/abi"
 	"internal/bytealg"
 	"internal/goarch"
+	"internal/runtime/math"
+	"internal/runtime/strconv"
 	"internal/runtime/sys"
 	"unsafe"
 )
@@ -391,77 +393,6 @@ func gostringn(p *byte, l int) string {
 	return s
 }
 
-const (
-	maxUint64 = ^uint64(0)
-	maxInt64  = int64(maxUint64 >> 1)
-)
-
-// atoi64 parses an int64 from a string s.
-// The bool result reports whether s is a number
-// representable by a value of type int64.
-func atoi64(s string) (int64, bool) {
-	if s == "" {
-		return 0, false
-	}
-
-	neg := false
-	if s[0] == '-' {
-		neg = true
-		s = s[1:]
-	}
-
-	un := uint64(0)
-	for i := 0; i < len(s); i++ {
-		c := s[i]
-		if c < '0' || c > '9' {
-			return 0, false
-		}
-		if un > maxUint64/10 {
-			// overflow
-			return 0, false
-		}
-		un *= 10
-		un1 := un + uint64(c) - '0'
-		if un1 < un {
-			// overflow
-			return 0, false
-		}
-		un = un1
-	}
-
-	if !neg && un > uint64(maxInt64) {
-		return 0, false
-	}
-	if neg && un > uint64(maxInt64)+1 {
-		return 0, false
-	}
-
-	n := int64(un)
-	if neg {
-		n = -n
-	}
-
-	return n, true
-}
-
-// atoi is like atoi64 but for integers
-// that fit into an int.
-func atoi(s string) (int, bool) {
-	if n, ok := atoi64(s); n == int64(int(n)) {
-		return int(n), ok
-	}
-	return 0, false
-}
-
-// atoi32 is like atoi but for integers
-// that fit into an int32.
-func atoi32(s string) (int32, bool) {
-	if n, ok := atoi64(s); n == int64(int32(n)) {
-		return int32(n), ok
-	}
-	return 0, false
-}
-
 // parseByteCount parses a string that represents a count of bytes.
 //
 // s must match the following regular expression:
@@ -483,7 +414,7 @@ func parseByteCount(s string) (int64, bool) {
 	// Handle the easy non-suffix case.
 	last := s[len(s)-1]
 	if last >= '0' && last <= '9' {
-		n, ok := atoi64(s)
+		n, ok := strconv.Atoi64(s)
 		if !ok || n < 0 {
 			return 0, false
 		}
@@ -498,7 +429,7 @@ func parseByteCount(s string) (int64, bool) {
 	// The one before that must always be a digit or 'i'.
 	if c := s[len(s)-2]; c >= '0' && c <= '9' {
 		// Trivial 'B' suffix.
-		n, ok := atoi64(s[:len(s)-1])
+		n, ok := strconv.Atoi64(s[:len(s)-1])
 		if !ok || n < 0 {
 			return 0, false
 		}
@@ -529,17 +460,17 @@ func parseByteCount(s string) (int64, bool) {
 	for i := 0; i < power; i++ {
 		m *= 1024
 	}
-	n, ok := atoi64(s[:len(s)-3])
+	n, ok := strconv.Atoi64(s[:len(s)-3])
 	if !ok || n < 0 {
 		return 0, false
 	}
 	un := uint64(n)
-	if un > maxUint64/m {
+	if un > math.MaxUint64/m {
 		// Overflow.
 		return 0, false
 	}
 	un *= m
-	if un > uint64(maxInt64) {
+	if un > uint64(math.MaxInt64) {
 		// Overflow.
 		return 0, false
 	}
diff --git a/src/runtime/string_test.go b/src/runtime/string_test.go
index cfc0ad7cde..522a502a1c 100644
--- a/src/runtime/string_test.go
+++ b/src/runtime/string_test.go
@@ -390,98 +390,6 @@ func TestString2Slice(t *testing.T) {
 
 const intSize = 32 << (^uint(0) >> 63)
 
-type atoi64Test struct {
-	in  string
-	out int64
-	ok  bool
-}
-
-var atoi64tests = []atoi64Test{
-	{"", 0, false},
-	{"0", 0, true},
-	{"-0", 0, true},
-	{"1", 1, true},
-	{"-1", -1, true},
-	{"12345", 12345, true},
-	{"-12345", -12345, true},
-	{"012345", 12345, true},
-	{"-012345", -12345, true},
-	{"12345x", 0, false},
-	{"-12345x", 0, false},
-	{"98765432100", 98765432100, true},
-	{"-98765432100", -98765432100, true},
-	{"20496382327982653440", 0, false},
-	{"-20496382327982653440", 0, false},
-	{"9223372036854775807", 1<<63 - 1, true},
-	{"-9223372036854775807", -(1<<63 - 1), true},
-	{"9223372036854775808", 0, false},
-	{"-9223372036854775808", -1 << 63, true},
-	{"9223372036854775809", 0, false},
-	{"-9223372036854775809", 0, false},
-}
-
-func TestAtoi(t *testing.T) {
-	switch intSize {
-	case 32:
-		for i := range atoi32tests {
-			test := &atoi32tests[i]
-			out, ok := runtime.Atoi(test.in)
-			if test.out != int32(out) || test.ok != ok {
-				t.Errorf("atoi(%q) = (%v, %v) want (%v, %v)",
-					test.in, out, ok, test.out, test.ok)
-			}
-		}
-	case 64:
-		for i := range atoi64tests {
-			test := &atoi64tests[i]
-			out, ok := runtime.Atoi(test.in)
-			if test.out != int64(out) || test.ok != ok {
-				t.Errorf("atoi(%q) = (%v, %v) want (%v, %v)",
-					test.in, out, ok, test.out, test.ok)
-			}
-		}
-	}
-}
-
-type atoi32Test struct {
-	in  string
-	out int32
-	ok  bool
-}
-
-var atoi32tests = []atoi32Test{
-	{"", 0, false},
-	{"0", 0, true},
-	{"-0", 0, true},
-	{"1", 1, true},
-	{"-1", -1, true},
-	{"12345", 12345, true},
-	{"-12345", -12345, true},
-	{"012345", 12345, true},
-	{"-012345", -12345, true},
-	{"12345x", 0, false},
-	{"-12345x", 0, false},
-	{"987654321", 987654321, true},
-	{"-987654321", -987654321, true},
-	{"2147483647", 1<<31 - 1, true},
-	{"-2147483647", -(1<<31 - 1), true},
-	{"2147483648", 0, false},
-	{"-2147483648", -1 << 31, true},
-	{"2147483649", 0, false},
-	{"-2147483649", 0, false},
-}
-
-func TestAtoi32(t *testing.T) {
-	for i := range atoi32tests {
-		test := &atoi32tests[i]
-		out, ok := runtime.Atoi32(test.in)
-		if test.out != out || test.ok != ok {
-			t.Errorf("atoi32(%q) = (%v, %v) want (%v, %v)",
-				test.in, out, ok, test.out, test.ok)
-		}
-	}
-}
-
 func TestParseByteCount(t *testing.T) {
 	for _, test := range []struct {
 		in  string