From 3452afee29f2d36af8c0fc61ef34df8823e796ae Mon Sep 17 00:00:00 2001
From: v1rtl <hi@v1rtl.site>
Date: Tue, 29 Sep 2026 12:30:40 +0200
Subject: [PATCH 1/2] runtime: add remaining MemStats fields for API
 compatibility

Adds the MemStats fields upstream Go defines that TinyGo did not have:
Lookups, StackInuse, StackSys, MSpanInuse, MSpanSys, MCacheInuse,
MCacheSys, BuckHashSys, OtherSys, NextGC and GCCPUFraction.

TinyGo has no runtime structures for these to describe, so they always
report 0 rather than carry made up values. They exist so that packages
reading MemStats can be compiled.

github.com/prometheus/client_golang fails to type check against TinyGo
because these fields are missing. See #3879.
---
 src/runtime/mstats.go | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/src/runtime/mstats.go b/src/runtime/mstats.go
index 4271bab9a4..aceda6a4ec 100644
--- a/src/runtime/mstats.go
+++ b/src/runtime/mstats.go
@@ -4,6 +4,9 @@ package runtime
 
 // Subset of memory statistics from upstream Go.
 // Works with conservative gc only.
+//
+// Fields tracking runtime structures that TinyGo does not have are present for
+// API compatibility only and always report 0.
 
 // A MemStats records statistics about the memory allocator.
 type MemStats struct {
@@ -21,6 +24,10 @@ type MemStats struct {
 	// heap, stacks, and other internal data structures.
 	Sys uint64
 
+	// Lookups is the number of pointer lookups performed by the
+	// runtime. Unused, as in upstream Go.
+	Lookups uint64
+
 	// Heap memory statistics.
 
 	// HeapAlloc is bytes of allocated heap objects.
@@ -80,11 +87,47 @@ type MemStats struct {
 	// structures that are not allocated from heap memory (usually
 	// because they are part of implementing the heap).
 
+	// StackInuse is bytes in stack spans.
+	StackInuse uint64
+
+	// StackSys is bytes of stack memory obtained from the OS.
+	StackSys uint64
+
+	// MSpanInuse is bytes of allocated mspan structures.
+	MSpanInuse uint64
+
+	// MSpanSys is bytes of memory obtained from the OS for mspan
+	// structures.
+	MSpanSys uint64
+
+	// MCacheInuse is bytes of allocated mcache structures.
+	MCacheInuse uint64
+
+	// MCacheSys is bytes of memory obtained from the OS for mcache
+	// structures.
+	MCacheSys uint64
+
+	// BuckHashSys is bytes of memory in profiling bucket hash tables.
+	BuckHashSys uint64
+
 	// GCSys is bytes of memory in garbage collection metadata.
 	GCSys uint64
 
+	// OtherSys is bytes of memory in miscellaneous off-heap runtime
+	// allocations.
+	OtherSys uint64
+
+	// Garbage collector statistics.
+
+	// NextGC is the target heap size of the next GC cycle.
+	NextGC uint64
+
 	// NumGC is the number of completed GC cycles.
 	//
 	// The leaking collector never collects, so it always reports 0.
 	NumGC uint32
+
+	// GCCPUFraction is the fraction of available CPU time used by the GC
+	// since the program started.
+	GCCPUFraction float64
 }

From ef4d9e8aff6bf71825de86de95b9a228d5d8abbe Mon Sep 17 00:00:00 2001
From: v1rtl <hi@v1rtl.site>
Date: Tue, 29 Sep 2026 12:30:40 +0200
Subject: [PATCH 2/2] runtime: add ThreadCreateProfile stub

Adds runtime.StackRecord and a runtime.ThreadCreateProfile stub that
always reports an empty profile, matching the existing
SetBlockProfileRate and SetMutexProfileFraction stubs.

github.com/prometheus/client_golang calls ThreadCreateProfile to count
OS threads. See #3879.
---
 src/runtime/debug.go | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/runtime/debug.go b/src/runtime/debug.go
index 62f6727f71..e8faec8cb7 100644
--- a/src/runtime/debug.go
+++ b/src/runtime/debug.go
@@ -26,3 +26,25 @@ func SetBlockProfileRate(rate int) {
 func SetMutexProfileFraction(rate int) int {
 	return 0
 }
+
+// A StackRecord describes a single execution stack.
+type StackRecord struct {
+	Stack0 [32]uintptr // stack trace for this record, ends at first 0 entry
+}
+
+// Stack returns the stack trace associated with the record, a prefix of
+// r.Stack0.
+func (r *StackRecord) Stack() []uintptr {
+	for i, v := range r.Stack0 {
+		if v == 0 {
+			return r.Stack0[0:i]
+		}
+	}
+	return r.Stack0[0:]
+}
+
+// Stub for ThreadCreateProfile, always reports an empty profile. TinyGo has no
+// thread creation profiler.
+func ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
+	return 0, true
+}