Builds fails on 32 bit systems

[misthios]

Hello,

I was updating the minify package in the Alpine Linux repos from 1.20.24 to 1.20.28 when I noticed that most if not all 32bit systems failed (log: https://gitlab.alpinelinux.org/Misthios/aports/-/jobs/1394860 ) with the same error:

# github.com/tdewolff/minify/v2/bindings/js
bindings/js/minify.go:28:12: invalid array length 1 << 32 (untyped int constant 4294967296)
bindings/js/minify.go:37:12: invalid array length 1 << 32 (untyped int constant 4294967296)
# github.com/tdewolff/minify/v2/bindings/py
bindings/py/minify.go:28:12: invalid array length 1 << 32 (untyped int constant 4294967296)
bindings/py/minify.go:37:12: invalid array length 1 << 32 (untyped int constant 4294967296)

I have made some changes to those file to get the build passing (log: https://gitlab.alpinelinux.org/Misthios/aports/-/jobs/1395003 ).
But since those changed are untested since I do not use those bindings.

Here are the changes:

--- /bindings/py/minify.go
+++ /bindings/py/minify.go
@@ -25,7 +25,10 @@
 }
 
 func goBytes(str *C.char, length C.longlong) []byte {
-	return (*[1 << 32]byte)(unsafe.Pointer(str))[:length:length]
+	unsafePtr := unsafe.Pointer(str)
+	byteSlice := unsafe.Slice((*byte)(unsafePtr), length)
+
+	return byteSlice
 }
 
 func goStringArray(carr **C.char, length C.longlong) []string {
@@ -34,11 +37,12 @@
 	}
 
 	strs := make([]string, length)
-	arr := (*[1 << 32]*C.char)(unsafe.Pointer(carr))[:length:length]
 	for i := 0; i < int(length); i++ {
-		strs[i] = C.GoString(arr[i])
+		cstr := *(**C.char)(unsafe.Pointer(uintptr(unsafe.Pointer(carr)) + uintptr(i)*unsafe.Sizeof(*carr)))
+		strs[i] = C.GoString(cstr)
 	}
 	return strs
+
 }
 
 //export minifyConfig
--- /bindings/js/minify.go
+++ /bindings/js/minify.go
@@ -25,7 +25,11 @@
 }
 
 func goBytes(str *C.char, length C.longlong) []byte {
-	return (*[1 << 32]byte)(unsafe.Pointer(str))[:length:length]
+	unsafePtr := unsafe.Pointer(str)
+	byteSlice := unsafe.Slice((*byte)(unsafePtr), length)
+	
+	return byteSlice
+
 }
 
 func goStringArray(carr **C.char, length C.longlong) []string {
@@ -34,11 +38,13 @@
 	}
 
 	strs := make([]string, length)
-	arr := (*[1 << 32]*C.char)(unsafe.Pointer(carr))[:length:length]
 	for i := 0; i < int(length); i++ {
-		strs[i] = C.GoString(arr[i])
+		cstr := *(**C.char)(unsafe.Pointer(uintptr(unsafe.Pointer(carr)) + uintptr(i)*unsafe.Sizeof(*carr)))
+		strs[i] = C.GoString(cstr)
 	}
+
 	return strs
+
 }
 
 //export minifyConfig

[tdewolff]

Thanks for the heads up! I believe we can just convert the 32 to 31, it's an upper limit on how long a slice can be (which is actually 1<<31 for 32 bit systems since Len() returns an int).

[tdewolff]

Can you try v2.20.29 and tell me if it works?

[misthios]

Hello,

the new versions gives the same error type but different value

# github.com/tdewolff/minify/v2/bindings/py
bindings/py/minify.go:28:12: invalid array length 1 << 31 (untyped int constant 2147483648)
bindings/py/minify.go:37:12: invalid array length 1 << 31 (untyped int constant 2147483648)
# github.com/tdewolff/minify/v2/bindings/js
bindings/js/minify.go:28:12: invalid array length 1 << 31 (untyped int constant 2147483648)
bindings/js/minify.go:37:12: invalid array length 1 << 31 (untyped int constant 2147483648)

[tdewolff]

Off-by-one error, please check v2.20.30!

[misthios]

Hello,

the 32bit build is unfortunately still broken.

1. the 2.20.30 commit only fixes one instance of the previous problem:

the goStringArray has the new -1, the goBytes still has 31 

2. after patching 1 we get a new problem which can be seen in the screenshot below (i only patched the python bindings for problem 1).

[tdewolff]

Must have been late, how does v2.20.31 do?

[misthios]

Hello,

I still get the same result unfortunately:

[tdewolff]

I really hope this is now fixed in v2.20.32, I have no idea why the address space for 32-bit systems is not math.MaxInt32-1 == 1<<31 - 1...

[misthios]

Hello,

2.20.32 seems to be working

Thank you :)