Fix segment size validation for imported memories (#1745)

Without this wasm-opt can't operation on emscripten-produced
SIDE_MODULES's which have zero sized memory imports.

Technically is not a validation failure if you have segments that
are larger than your initial memory, regardless of whether you
import them.

For non-imported memories it can be helpful though, so leaving it
in to catch those errors.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index fbd31b920..769f17d59 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -974,9 +974,14 @@ static void validateMemory(Module& module, ValidationInfo& info) {
   if (curr.shared) info.shouldBeTrue(info.features & Feature::Atomics, "memory", "memory is shared, but atomics are disabled");
   for (auto& segment : curr.segments) {
     if (!info.shouldBeEqual(segment.offset->type, i32, segment.offset, "segment offset should be i32")) continue;
-    info.shouldBeTrue(checkOffset(segment.offset, segment.data.size(), module.memory.initial * Memory::kPageSize), segment.offset, "segment offset should be reasonable");
+    info.shouldBeTrue(checkOffset(segment.offset, segment.data.size(), curr.initial * Memory::kPageSize), segment.offset, "segment offset should be reasonable");
     Index size = segment.data.size();
-    info.shouldBeTrue(size <= curr.initial * Memory::kPageSize, segment.data.size(), "segment size should fit in memory (initial)");
+    // If the memory is imported we don't actually know its initial size.
+    // Specifically wasm dll's import a zero sized memory which is perfectly
+    // valid.
+    if (!curr.imported()) {
+      info.shouldBeTrue(size <= curr.initial * Memory::kPageSize, segment.data.size(), "segment size should fit in memory (initial)");
+    }
     if (segment.offset->is<Const>()) {
       Index start = segment.offset->cast<Const>()->value.geti32();
       Index end = start + size;