Introduce multi-engine franken-build.

BUILD

@@ -127,22 +127,54 @@ cc_library(
     ],
 )
 
-cc_library(
-    name = "wasmtime_lib",
+genrule(
+    name = "prefixed_wasmtime_sources",
     srcs = [
-        "src/common/types.h",
         "src/wasmtime/types.h",
         "src/wasmtime/wasmtime.cc",
     ],
+    outs = [
+        "src/wasmtime/prefixed_types.h",
+        "src/wasmtime/prefixed_wasmtime.cc",
+    ],
+    cmd = """
+        for file in $(SRCS); do
+           sed -e 's/wasm_/wasmtime_wasm_/g' \
+               -e 's/wasmtime\\/types.h/wasmtime\\/prefixed_types.h/g' \
+           $$file >$(@D)/$$(dirname $$file)/prefixed_$$(basename $$file)
+        done
+        """,
+)
+
+cc_library(
+    name = "wasmtime_lib",
+    srcs = [
+        "src/common/types.h",
+    ] + select({
+        "@proxy_wasm_cpp_host//bazel:multiengine": [
+            "src/wasmtime/prefixed_types.h",
+            "src/wasmtime/prefixed_wasmtime.cc",
+        ],
+        "//conditions:default": [
+            "src/wasmtime/types.h",
+            "src/wasmtime/wasmtime.cc",
+        ],
+    }),
     hdrs = ["include/proxy-wasm/wasmtime.h"],
     defines = [
         "PROXY_WASM_HAS_RUNTIME_WASMTIME",
         "PROXY_WASM_HOST_ENGINE_WASMTIME",
     ],
     deps = [
         ":wasm_vm_headers",
-        "//external:wasmtime",
-    ],
+    ] + select({
+        "@proxy_wasm_cpp_host//bazel:multiengine": [
+            "//external:prefixed_wasmtime",
+        ],
+        "//conditions:default": [
+            "//external:wasmtime",
+        ],
+    }),
 )
 
 cc_library(

bazel/BUILD

@@ -20,6 +20,11 @@ config_setting(
     values = {"define": "engine=wavm"},
 )
 
+config_setting(
+    name = "multiengine",
+    values = {"define": "engine=multi"},
+)
+
 config_setting(
     name = "requested_crypto_system",
     values = {"define": "crypto=system"},

bazel/external/v8.patch

@@ -1,7 +1,8 @@
-# Disable pointer compression (limits the maximum number of WasmVMs).
+# 1. Disable pointer compression (limits the maximum number of WasmVMs).
+# 2. Don't expose Wasm C API (only Wasm C++ API).
 
 diff --git a/BUILD.bazel b/BUILD.bazel
-index 1cc0121e60..4947c1dba2 100644
+index 5fb10d3940..a19930d36e 100644
 --- a/BUILD.bazel
 +++ b/BUILD.bazel
 @@ -161,7 +161,7 @@ v8_int(
@@ -13,3 +14,22 @@ index 1cc0121e60..4947c1dba2 100644
  )
 
  # Default setting for v8_enable_pointer_compression.
+diff --git a/src/wasm/c-api.cc b/src/wasm/c-api.cc
+index ce3f569fd5..dc8a4c4f6a 100644
+--- a/src/wasm/c-api.cc
++++ b/src/wasm/c-api.cc
+@@ -2238,6 +2238,8 @@ auto Instance::exports() const -> ownvec<Extern> {
+
+ }  // namespace wasm
+
++#if 0
++
+ // BEGIN FILE wasm-c.cc
+
+ extern "C" {
+@@ -3257,3 +3259,5 @@ wasm_instance_t* wasm_frame_instance(const wasm_frame_t* frame) {
+ #undef WASM_DEFINE_SHARABLE_REF
+
+ }  // extern "C"
++
++#endif

bazel/external/wasm-c-api.BUILD

@@ -14,3 +14,48 @@ cc_library(
         "@com_github_bytecodealliance_wasmtime//:rust_c_api",
     ],
 )
+
+genrule(
+    name = "prefixed_wasmtime_c_api_headers",
+    srcs = [
+        "include/wasm.h",
+    ],
+    outs = [
+        "wasmtime/include/wasm.h",
+    ],
+    cmd = """
+        sed -e 's/\\ wasm_/\\ wasmtime_wasm_/g' \
+            -e 's/\\*wasm_/\\*wasmtime_wasm_/g' \
+            -e 's/(wasm_/(wasmtime_wasm_/g'     \
+        $(<) >$@
+        """,
+)
+
+genrule(
+    name = "prefixed_wasmtime_c_api_lib",
+    srcs = [
+        "@com_github_bytecodealliance_wasmtime//:rust_c_api",
+    ],
+    outs = [
+        "prefixed_wasmtime_c_api.a",
+    ],
+    cmd = """
+        for symbol in $$(nm -P $(<) 2>/dev/null | grep -E ^_?wasm_ | cut -d" " -f1); do
+            echo $$symbol | sed -r 's/^(_?)(wasm_[a-z_]+)$$/\\1\\2 \\1wasmtime_\\2/' >>prefixed
+        done
+        # This should be OBJCOPY, but bazel-zig-cc doesn't define it.
+        objcopy --redefine-syms=prefixed $(<) $@
+        """,
+    toolchains = ["@bazel_tools//tools/cpp:current_cc_toolchain"],
+)
+
+cc_library(
+    name = "prefixed_wasmtime_lib",
+    srcs = [
+        ":prefixed_wasmtime_c_api_lib",
+    ],
+    hdrs = [
+        ":prefixed_wasmtime_c_api_headers",
+    ],
+    linkstatic = 1,
+)

bazel/repositories.bzl

@@ -192,6 +192,11 @@ def proxy_wasm_cpp_host_repositories():
         actual = "@com_github_webassembly_wasm_c_api//:wasmtime_lib",
     )
 
+    native.bind(
+        name = "prefixed_wasmtime",
+        actual = "@com_github_webassembly_wasm_c_api//:prefixed_wasmtime_lib",
+    )
+
     # WAVM with dependencies.
 
     maybe(

bazel/select.bzl

@@ -15,23 +15,27 @@
 def proxy_wasm_select_engine_v8(xs):
     return select({
         "@proxy_wasm_cpp_host//bazel:engine_v8": xs,
+        "@proxy_wasm_cpp_host//bazel:multiengine": xs,
         "//conditions:default": [],
     })
 
 def proxy_wasm_select_engine_wamr(xs):
     return select({
         "@proxy_wasm_cpp_host//bazel:engine_wamr": xs,
+        "@proxy_wasm_cpp_host//bazel:multiengine": xs,
         "//conditions:default": [],
     })
 
 def proxy_wasm_select_engine_wasmtime(xs):
     return select({
         "@proxy_wasm_cpp_host//bazel:engine_wasmtime": xs,
+        "@proxy_wasm_cpp_host//bazel:multiengine": xs,
         "//conditions:default": [],
     })
 
 def proxy_wasm_select_engine_wavm(xs):
     return select({
         "@proxy_wasm_cpp_host//bazel:engine_wavm": xs,
+        "@proxy_wasm_cpp_host//bazel:multiengine": xs,
         "//conditions:default": [],
     })

src/wasmtime/wasmtime.cc

@@ -24,7 +24,6 @@
 #include <unordered_map>
 #include <vector>
 
-#include "include/proxy-wasm/wasm_vm.h"
 #include "src/wasmtime/types.h"
 
 #include "wasmtime/include/wasm.h"