Added comments

2 files changed, 15 insertions, 0 deletions

diff --git a/tools/codegen/core/gen_hpack_tables.c b/tools/codegen/core/gen_hpack_tables.c
index 21667f0651..48398bebd5 100644
--- a/tools/codegen/core/gen_hpack_tables.c
+++ b/tools/codegen/core/gen_hpack_tables.c
@@ -71,6 +71,11 @@ static unsigned char prefix_mask(unsigned char prefix_len) {
   unsigned char i;
   unsigned char out = 0;
   for (i = 0; i < prefix_len; i++) {
+    /* NB: the following integer arithmetic operation needs to be in its
+     * expanded form due to the "integral promotion" performed (see section
+     * 3.2.1.1 of the C89 draft standard), which in this case upcasts the result
+     * of the bitwise OR to "unsigned". A cast to the smaller container type is
+     * then required to avoid the compiler warning */
     out = (unsigned char)(out | (unsigned char)(1 << (7 - i)));
   }
   return out;
@@ -92,6 +97,11 @@ static void generate_first_byte_lut(void) {
     chrspec = NULL;
     for (j = 0; j < num_fields; j++) {
       if ((prefix_mask(fields[j].prefix_length) & i) == fields[j].prefix) {
+        /* NB: the following integer arithmetic operation needs to be in its
+         * expanded form due to the "integral promotion" performed (see section
+         * 3.2.1.1 of the C89 draft standard), which in this case upcasts the
+         * result of the bitwise AND to "unsigned". A cast to the smaller
+         * container type is then required to avoid the compiler warning */
         suffix = (unsigned char)(suffix_mask(fields[j].prefix_length) &
                                  (unsigned char)i);
         if (suffix == suffix_mask(fields[j].prefix_length)) {
diff --git a/tools/codegen/core/gen_legal_metadata_characters.c b/tools/codegen/core/gen_legal_metadata_characters.c
index 5783c3ff69..3718916577 100644
--- a/tools/codegen/core/gen_legal_metadata_characters.c
+++ b/tools/codegen/core/gen_legal_metadata_characters.c
@@ -41,6 +41,11 @@ static unsigned char legal_bits[256 / 8];
 static void legal(int x) {
   int byte = x / 8;
   int bit = x % 8;
+  /* NB: the following integer arithmetic operation needs to be in its
+   * expanded form due to the "integral promotion" performed (see section
+   * 3.2.1.1 of the C89 draft standard), which in this case upcasts the result
+   * of the bitwise OR to "unsigned". A cast to the smaller container type is
+   * then required to avoid the compiler warning */
   legal_bits[byte] =
       (unsigned char)((legal_bits[byte] | (unsigned char)(1 << bit)));
 }