Fix appending-zero issues

[mehdi_amini]

Can you please elaborate with some context in the description?

Also is there a unit-test that can exercise the issue?

[GeorgeLyon]

Sorry I abandoned this because the situation I thought I was able to reproduce, stopped reproducing. I think the underlying issue was unrelated

mlir/lib/CAPI/IR/IR.cpp

MlirOperationState mlirOperationStateGet(MlirStringRef name, MlirLocation loc) {
   state.nSuccessors = 0;
   state.successors = nullptr;
   state.nAttributes = 0;
   state.attributes = nullptr;
   return state;
 }
 
 #define APPEND_ELEMS(type, sizeName, elemName)                                 \
-  state->elemName =                                                            \
-      (type *)realloc(state->elemName, (state->sizeName + n) * sizeof(type));  \
-  memcpy(state->elemName + state->sizeName, elemName, n * sizeof(type));       \
-  state->sizeName += n;
+  if (n > 0) {                                                                 \
+    state->elemName = (type *)realloc(state->elemName,                         \
+                                      (state->sizeName + n) * sizeof(type));   \
+    memcpy(state->elemName + state->sizeName, elemName, n * sizeof(type));     \
+    state->sizeName += n;                                                      \
+  }
 
 void mlirOperationStateAddResults(MlirOperationState *state, intptr_t n,
                                   MlirType const *results) {
   APPEND_ELEMS(MlirType, nResults, results);
 }
 
 void mlirOperationStateAddOperands(MlirOperationState *state, intptr_t n,
                                    MlirValue const *operands) {