More verbose -print-allocs messages. Initial commit. by ebak · Pull Request #5504 · tinygo-org/tinygo

ebak · 2026-07-06T19:05:28Z

This change intends to provide more verbose -print-allocs messages by naming the escaping intermediate variable or type.
Currently it is tested only with the unit tests.

Here are the modified messages, generated by allocs_test.go:

makeslice.buf size is not constant
makeslice4 size 300 exceeds maximum stack allocation size 256
makeslice6 escapes at line 30
FloatType escapes at line 37
varargs12 escapes at line 44
slicelit14 escapes at line 47
n4 escapes at line 51
n5 escapes at line 51
makeslice escapes at line 108
b escapes at line 117
Arg 0 of main.scaleVector3() call escapes at line 122
b escapes at unknown line

dgryski

Seems good but someone else a bit more familiar with this code should take a look.

ebak · 2026-07-12T10:09:30Z

Now the messages from the allocs_test.go unit test are looking like this:

allocs2.go:26: makeslice.buf size is not constant
allocs2.go:28: makeslice4 size 300 exceeds maximum stack allocation size 256
allocs2.go:31: makeslice6 escapes at line 32
allocs2.go:38: Arg 0 (type: basic:complex128) of main.useInterface() escapes at line 40
allocs2.go:43: Arg 0 (type: array:3:basic:int32) of main.useInterface() escapes at line 43
allocs2.go:50: varargs12 escapes at line 50
allocs2.go:52: slicelit14 escapes at line 53
allocs2.go:55: n4 escapes at line 57
allocs2.go:56: n5 escapes at line 57
allocs2.go:132: makeslice escapes at line 133
allocs2.go:139: b escapes at line 142
allocs2.go:148: Arg 0 of main.scaleVector3() escapes at line 149
allocs2.go:150: complit1 escapes at line 151
allocs2.go:150: complit2 escapes at line 151
allocs2.go:156: Arg 1 (type: pointer:named:main.vector3) of main.useInterfaces() escapes at line 156
allocs2.go:156: Arg 4 (type: pointer:named:main.vector3) of main.useInterfaces() escapes at line 156
allocs2.go:160: Arg 1 (type: pointer:named:main.vector3) of main.useInterfaces() escapes at line 160
allocs2.go:160: Arg 4 (type: pointer:named:main.vector3) of main.useInterfaces() escapes at line 160
allocs2.go:171: b escapes at unknown line
allocs2.go:179: varargs escapes at line 179
allocs2.go:184: main.theError escapes at line 184
allocs2.go:188: main.theError escapes at line 188
allocs2.go:193: array:3:basic:int32 escapes at line 193

I also executed this -print-allocs on one of my projects and I got these results:

heap/storage/unsafe_arraylist.go:64:30: heap allocation: 16 bytes escapes at line 64
heap/checks/string_test.go:35:30: heap allocation: 16 bytes escapes at line 35
heap/checks/string_test.go:13:2: heap allocation: alloc escapes at line 16   // --- here "alloc" is a variable name
heap/checks/string_test.go:10:17: heap allocation: t1 escapes at line 16
heap/checks/string_test.go:48:79: heap allocation: 96 bytes escapes at line 48
heap/checks/string_test.go:45:21: heap allocation: 16 bytes escapes at line 48
heap/checks/str_test.go:24:3: heap allocation: str escapes at line 14
heap/checks/str_test.go:17:2: heap allocation: alloc escapes at line 14      // --- here "alloc" is a variable name
heap/checks/utils.go:16:25: heap allocation: 16 bytes escapes at line 16
heap/internal/holecache/simple/simple.go:22:15: heap allocation: complit escapes at line 22
heap/internal/heap/allocator.go:47:14: heap allocation: makeslice.buf escapes at line 51
heap/internal/heap/allocator.go:235:20: heap allocation: heap/internal/heap.AllocError escapes at line 235
heap/internal/heap/allocator.go:218:20: heap allocation: heap/internal/heap.AllocError escapes at line 218
heap/internal/heap/allocator.go:213:20: heap allocation: heap/internal/heap.AllocError escapes at line 213
heap/internal/heap/allocator.go:179:22: heap allocation: heap/internal/heap.AllocError escapes at line 179
heap/internal/heap/allocator.go:386:20: heap allocation: heap/internal/heap.AllocError escapes at line 386
heap/internal/heap/allocator.go:374:23: heap allocation: heap/internal/heap.AllocError escapes at line 374
heap/internal/heap/allocator.go:311:31: heap allocation: heap/internal/heap.AllocError escapes at line 314
heap/internal/heap/allocator.go:199:29: heap allocation: heap/internal/heap.AllocError escapes at line 182
heap/internal/heap/allocator.go:196:33: heap allocation: heap/internal/heap.AllocError escapes at line 196

Of course it is far from being perfect, but probably there is more possibility for mining out the name and/or type of the escaped object from LLVM IR and this change could be a stub for that.

b0ch3nski · 2026-07-12T11:59:21Z

+	return
+}
+
+func dumpIR(hdr string, instCnt int, fstInst llvm.Value) {


Seems dumpIR is unused?

Yes, anyone who touches this code can use it for debugging.

Please remove test code like this, it leads to clutter.

aykevl

While I agree with the idea here, the PR does need some cleanup before merging (lots of debugging code, commented out code, etc).

Also, the values printed here are mostly internal compiler values that I'm afraid will mostly be confusing to users. I recommend instead to look into adding a string attribute to the runtime.alloc call, that can then be retrieved during the printing to get the type (and perhaps the reason why it was allocated, such as "making a slice"). I'd prefer if those internal values would stay internal and we show something actually useful to users. It would be nice to have a message like "[]byte slice allocated at line X" which would be possible this way.

aykevl · 2026-07-13T10:47:37Z

+	return
+}
+
+func dumpIR(hdr string, instCnt int, fstInst llvm.Value) {


Please remove test code like this, it leads to clutter.

aykevl · 2026-07-13T10:50:24Z

+	theErr := theError{}
+	var err error = theErr
+	theErr.set("hello")
+	println(err.Error())


Debug code, remove please.

@aykevl, thanks for the advise. I made an initial implementation. Unfortunately not all alloc calls get the attributes.
I have found 2 places in compiler/compiler.go, where setting attributes are reflected in LLVM IR alloc calls. These places are in builder.createExpr(expr ssa.Value) in case *ssa.Alloc: and case *ssa.MakeSlice:.
I have also checked where builder.createAlloc() are used, but I haven't identified relevant places.

Now the test output looks like this:

allocs2.go:26: slice size is not constant allocs2.go:28: slice [300]byte size 300 exceeds maximum stack allocation size 256 allocs2.go:31: slice [4]int escapes at line 32 allocs2.go:38: Arg 0 (type: basic:complex128) of main.useInterface() escapes at line 40 // --- Fallback allocs2.go:43: Arg 0 (type: array:3:basic:int32) of main.useInterface() escapes at line 43 // --- Fallback allocs2.go:50: varargs [3]int escapes at line 50 allocs2.go:52: slice [3]int escapes at line 53 allocs2.go:55: n4 escapes at line 57 allocs2.go:56: n5 escapes at line 57 allocs2.go:127: slice [3]int escapes at line 128 allocs2.go:134: b escapes at line 137 allocs2.go:143: main.vector3 escapes at line 144 allocs2.go:145: main.vector3 escapes at line 146 allocs2.go:145: main.vector3 escapes at line 146 allocs2.go:151: main.vector3 escapes at line 151 allocs2.go:151: main.vector3 escapes at line 151 allocs2.go:155: main.vector3 escapes at line 155 allocs2.go:155: main.vector3 escapes at line 155 allocs2.go:166: b escapes at unknown line allocs2.go:174: varargs [1]any escapes at line 174 allocs2.go:179: main.theError escapes at line 179 allocs2.go:183: main.theError escapes at line 183 allocs2.go:188: array:3:basic:int32 escapes at line 188 // --- Fallback

Do you have idea for improvement?

More verbose -print-allocs messages. Initial commit.

9a1095c

dgryski reviewed Jul 6, 2026

View reviewed changes

More verbose -print-allocs: Fix in complex literal handling.

59d0c21

ebak marked this pull request as draft July 10, 2026 08:08

More verbose -print-allocs: better identification of heap allocated data

32be597

ebak marked this pull request as ready for review July 12, 2026 10:12

b0ch3nski reviewed Jul 12, 2026

View reviewed changes

aykevl requested changes Jul 13, 2026

View reviewed changes

ebak marked this pull request as draft July 13, 2026 15:24

More verbose -print-allocs: Initial commit of using attributes

4bc85ce

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More verbose -print-allocs messages. Initial commit.#5504

More verbose -print-allocs messages. Initial commit.#5504
ebak wants to merge 4 commits into
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ebak:print-allocs-verbose

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