Silence compiler warnings (#42056)

Author: vchuravy

src/cgutils.cpp

@@ -1711,8 +1711,8 @@ static jl_cgval_t typed_store(jl_codectx_t &ctx,
             Compare = Current;
             needloop = !isswapfield || Order != AtomicOrdering::NotAtomic;
         }
-        BasicBlock *BB;
-        PHINode *CmpPhi;
+        BasicBlock *BB = NULL;
+        PHINode *CmpPhi = NULL;
         if (needloop) {
             BasicBlock *From = ctx.builder.GetInsertBlock();
             BB = BasicBlock::Create(jl_LLVMContext, "xchg", ctx.f);
@@ -3303,8 +3303,8 @@ static jl_cgval_t emit_setfield(jl_codectx_t &ctx,
         jl_cgval_t oldval = rhs;
         if (!issetfield)
             oldval = emit_unionload(ctx, addr, ptindex, jfty, fsz, al, strct.tbaa, true);
-        Value *Success;
-        BasicBlock *DoneBB;
+        Value *Success = NULL;
+        BasicBlock *DoneBB = NULL;
         if (isreplacefield || ismodifyfield) {
             if (ismodifyfield) {
                 if (needlock)

src/codegen.cpp

@@ -6012,8 +6012,8 @@ static jl_returninfo_t get_specsig_function(jl_codectx_t &ctx, Module *M, String
 {
     jl_returninfo_t props = {};
     SmallVector<Type*, 8> fsig;
-    Type *rt;
-    Type *srt;
+    Type *rt = NULL;
+    Type *srt = NULL;
     if (jl_is_structtype(jlrettype) && jl_is_datatype_singleton((jl_datatype_t*)jlrettype)) {
         rt = T_void;
         props.cc = jl_returninfo_t::Register;

src/datatype.c

@@ -1712,7 +1712,7 @@ jl_value_t *replace_nth_field(jl_datatype_t *st, jl_value_t *v, size_t i, jl_val
         }
         else {
             jl_task_t *ct = jl_current_task;
-            uint8_t *psel;
+            uint8_t *psel = NULL;
             if (isunion) {
                 psel = &((uint8_t*)v)[offs + fsz - 1];
                 rty = jl_nth_union_component(rty, *psel);

src/gc.c

@@ -2564,7 +2564,7 @@ mark: {
             if (a->data == NULL || jl_array_len(a) == 0)
                 goto pop;
             if (flags.ptrarray) {
-                if (jl_tparam0(vt) == jl_symbol_type)
+                if ((jl_datatype_t*)jl_tparam0(vt) == jl_symbol_type)
                     goto pop;
                 size_t l = jl_array_len(a);
                 uintptr_t nptr = (l << 2) | (bits & GC_OLD);