diff --git a/breed/breed.sh b/breed/breed.sh
new file mode 100755
index 0000000..7f1b524
--- /dev/null
+++ b/breed/breed.sh
@@ -0,0 +1,85 @@
+#!/bin/bash -ex
+
+WASI_SDK_PATH=/opt/wasi-sdk
+CC=${WASI_SDK_PATH}/bin/clang
+
+cat >w2c2_main.c <<END
+#include <stdio.h>
+#include "w2c2_base.h"
+#include "wasi.h"
+#include "w2c2.h"
+
+void
+trap(
+    Trap trap
+) {
+    fprintf(stderr, "TRAP: %s\n", trapDescription(trap));
+    abort();
+}
+
+wasmMemory*
+wasiMemory(
+    void* instance
+) {
+    return w2c2_memory((w2c2Instance*)instance);
+}
+
+extern char** environ;
+
+/* Main */
+
+int main(int argc, char* argv[]) {
+    /* Initialize WASI */
+    if (!wasiInit(argc, argv, environ)) {
+        fprintf(stderr, "failed to init WASI\n");
+        return 1;
+    }
+
+    if (!wasiFileDescriptorAdd(-1, "/", NULL)) {
+        fprintf(stderr, "failed to add preopen\n");
+        return 1;
+    }
+
+    {
+        w2c2Instance instance;
+        w2c2Instantiate(&instance, NULL);
+        w2c2__start(&instance);
+        w2c2FreeInstance(&instance);
+    }
+
+    return 0;
+}
+END
+
+if ! [ -d build ]; then
+    mkdir build
+    cd build
+    mkdir w2c2
+    cd w2c2
+    CFLAGS="-Wl,--stack-first -Wl,-z,stack-size=1048576" cmake ../../../w2c2 -DCMAKE_TOOLCHAIN_FILE=${WASI_SDK_PATH}/share/cmake/wasi-sdk.cmake -DCMAKE_BUILD_TYPE=Debug
+    make
+    cd ..
+    mkdir wasi
+    cd wasi
+    CFLAGS="-Wl,--stack-first -Wl,-z,stack-size=1048576" cmake ../../../wasi -DCMAKE_TOOLCHAIN_FILE=${WASI_SDK_PATH}/share/cmake/wasi-sdk.cmake -DCMAKE_BUILD_TYPE=Debug
+    make
+    cd ../..
+fi
+
+rm -rf silly
+mkdir -p silly/gen1
+cp build/w2c2/w2c2 silly/gen1/w2c2.wasm
+
+function breed() {
+    genX=gen$1
+    genY=gen$(($1 + 1))
+    echo "=======> breeding ${genX} into ${genY}" >&2
+
+    mkdir -p silly/${genY}
+    wasmtime run --dir . "silly/${genX}/w2c2.wasm" "silly/${genX}/w2c2.wasm" "silly/${genY}/w2c2.c"
+    ${CC} -I../w2c2 -I../wasi -Isilly/${genY} build/wasi/libw2c2wasi.a silly/${genY}/w2c2.c w2c2_main.c -o silly/${genY}/w2c2.wasm
+}
+
+for gen in $(seq 1 10); do
+    breed "$gen"
+done
diff --git a/tests/Makefile b/tests/Makefile
index 52750f5..714d211 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -69,4 +69,4 @@ gen-%:
 	$(PYTHON3) gen.py $*
 
 clean:
-	-rm -f main.o test_*.o
+	-rm -f main.o test_*.o test_*.h
diff --git a/w2c2/CMakeLists.txt b/w2c2/CMakeLists.txt
index c5f27fa..dafb342 100644
--- a/w2c2/CMakeLists.txt
+++ b/w2c2/CMakeLists.txt
@@ -11,7 +11,7 @@ set(CMAKE_C_STANDARD 90)
 set(THREADS_PREFER_PTHREAD_FLAG ON)
 find_package(Threads)
 
-if(NOT DWARF_FOUND)
+if((NOT DWARF_FOUND) AND (NOT CMAKE_CROSSCOMPILING))
     find_package(PkgConfig)
     if(PKG_CONFIG_FOUND)
         pkg_check_modules(DWARF libdwarf)
diff --git a/w2c2/c.c b/w2c2/c.c
index 5961f78..bbaae5e 100644
--- a/w2c2/c.c
+++ b/w2c2/c.c
@@ -556,6 +556,7 @@ typedef struct WasmCFunctionWriter {
     const char* moduleName;
     WasmFunction function;
     Buffer* code;
+    U8* codeStart;
     U32 indent;
     bool ignore;
     bool pretty;
@@ -4425,6 +4426,7 @@ wasmCWriteFunctionBody(
         writer.moduleName = moduleName;
         writer.function = function;
         writer.code = &code;
+        writer.codeStart = code.data;
         writer.indent = 0;
         writer.ignore = false;
         writer.pretty = pretty;
diff --git a/w2c2/stringbuilder.c b/w2c2/stringbuilder.c
index bd4eb40..c7cd227 100644
--- a/w2c2/stringbuilder.c
+++ b/w2c2/stringbuilder.c
@@ -113,26 +113,9 @@ stringBuilderAppendU32(
     StringBuilder* stringBuilder,
     U32 value
 ) {
-    char temp[10];
-    char* tempPointer = temp;
-    char* buffer = NULL;
-
-    MUST (stringBuilderEnsureCapacity(stringBuilder, stringBuilder->length + 11))
-    buffer = stringBuilder->string + stringBuilder->length;
-
-    do {
-        *tempPointer++ = (char)(value % 10) + '0';
-        value /= 10;
-    } while (value > 0);
-
-    do {
-        *buffer++ = *--tempPointer;
-        stringBuilder->length++;
-    } while (tempPointer != temp);
-
-    *buffer = '\0';
-
-    return true;
+    char buffer[11];
+    const int length = sprintf(buffer, "%u", value);
+    return stringBuilderAppendSized(stringBuilder, buffer, (size_t) length);
 }
 
 bool
@@ -140,15 +123,9 @@ stringBuilderAppendI32(
     StringBuilder* stringBuilder,
     const I32 value
 ) {
-    U32 unsignedValue = (U32)value;
-    if (value < 0) {
-        MUST (stringBuilderEnsureCapacity(stringBuilder, stringBuilder->length + 1))
-        stringBuilder->string[stringBuilder->length] = '-';
-        stringBuilder->length++;
-
-        unsignedValue = ~unsignedValue + 1;
-    }
-    return stringBuilderAppendU32(stringBuilder, unsignedValue);
+    char buffer[12];
+    const int length = sprintf(buffer, "%i", value);
+    return stringBuilderAppendSized(stringBuilder, buffer, (size_t) length);
 }
 
 bool
@@ -156,26 +133,9 @@ stringBuilderAppendU64(
     StringBuilder* stringBuilder,
     U64 value
 ) {
-    char temp[20];
-    char* tempPointer = temp;
-    char* buffer = NULL;
-
-    MUST (stringBuilderEnsureCapacity(stringBuilder, stringBuilder->length + 21))
-    buffer = stringBuilder->string + stringBuilder->length;
-
-    do {
-        *tempPointer++ = (char)(value % 10) + '0';
-        value /= 10;
-    } while (value > 0);
-
-    do {
-        *buffer++ = *--tempPointer;
-        stringBuilder->length++;
-    } while (tempPointer != temp);
-
-    *buffer = '\0';
-
-    return true;
+    char buffer[21];
+    const int length = sprintf(buffer, "%llu", value);
+    return stringBuilderAppendSized(stringBuilder, buffer, (size_t) length);
 }
 
 bool
@@ -183,15 +143,9 @@ stringBuilderAppendI64(
     StringBuilder* stringBuilder,
     const I64 value
 ) {
-    U64 unsignedValue = (U64)value;
-    if (value < 0) {
-        MUST (stringBuilderEnsureCapacity(stringBuilder, stringBuilder->length + 1))
-        stringBuilder->string[stringBuilder->length] = '-';
-        stringBuilder->length++;
-
-        unsignedValue = ~unsignedValue + 1;
-    }
-    return stringBuilderAppendU64(stringBuilder, unsignedValue);
+    char buffer[22];
+    const int length = sprintf(buffer, "%lli", value);
+    return stringBuilderAppendSized(stringBuilder, buffer, (size_t) length);
 }
 
 bool