Fix -Werror=type-limits. (#15635)

I'm compiling cuDF as a part of another application and ran into errors from `-Werror=type-limits`. There are a few comparisons between unsigned types like `value < 0`, which is never true. This PR removes those impossible code paths.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - MithunR (https://github.com/mythrocks)
  - David Wendt (https://github.com/davidwendt)

URL: #15635

cpp/src/io/comp/cpu_unbz2.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2023, NVIDIA CORPORATION.
+ * Copyright (c) 2018-2024, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -221,7 +221,7 @@ int32_t bz2_decompress_block(unbz_state_s* s)
   if (getbits(s, 1)) return BZ_DATA_ERROR;  // blockRandomized not supported (old bzip versions)
 
   s->origPtr = getbits(s, 24);
-  if (s->origPtr < 0 || s->origPtr > 10 + 100000 * s->blockSize100k) return BZ_DATA_ERROR;
+  if (s->origPtr > 10 + 100000 * s->blockSize100k) return BZ_DATA_ERROR;
 
   // Receive the mapping table
   inUse16 = getbits(s, 16);
@@ -436,7 +436,7 @@ int32_t bz2_decompress_block(unbz_state_s* s)
   }
 
   // Now we know what nblock is, we can do a better sanity check on s->origPtr.
-  if (s->origPtr < 0 || s->origPtr >= nblock) return BZ_DATA_ERROR;
+  if (s->origPtr >= nblock) return BZ_DATA_ERROR;
 
   // compute the T^(-1) vector
   {

cpp/src/io/parquet/reader_impl_helpers.cpp

@@ -205,7 +205,6 @@ void metadata::sanitize_schema()
   // This code attempts to make this less messy for the code that follows.
 
   std::function<void(size_t)> process = [&](size_t schema_idx) -> void {
-    if (schema_idx < 0) { return; }
     auto& schema_elem = schema[schema_idx];
     if (schema_idx != 0 && schema_elem.type == UNDEFINED_TYPE) {
       auto const parent_type = schema[schema_elem.parent_idx].converted_type;
@@ -723,7 +722,6 @@ aggregate_reader_metadata::select_columns(std::optional<std::vector<std::string>
                        int schema_idx,
                        std::vector<cudf::io::detail::inline_column_buffer>& out_col_array,
                        bool has_list_parent) {
-      if (schema_idx < 0) { return false; }
       auto const& schema_elem = get_schema(schema_idx);
 
       // if schema_elem is a stub then it does not exist in the column_name_info and column_buffer