Be a bit safer with signed arithmetic, thus quieting some signed-overflow warnings from GCC (#1706)

* Avoid a signed overflow: check the range of `entry_ptr->age` before
increasing it instead of increasing it and then checking the range.
This quiets a GCC warning.

* Avoid the potential for signed overflow by rewriting expressions
`MAX(0, fwidth - n)` as `MAX(n, fwidth) - n` for various `n`.
This change quiets some GCC warnings.

* Change some local variables that cannot take sensible negative values
from signed to unsigned.  This quiets GCC warnings about potential
signed overflow.

* In a handful of instances, check the range of a signed integer before
increasing/decreasing it, just in case the increase/decrease overflows.
This quiets a handful of GCC signed-overflow warnings.

* Committing clang-format changes

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/H5Cimage.c b/src/H5Cimage.c
index ddf5f94..899d6d7 100644
--- a/src/H5Cimage.c
+++ b/src/H5Cimage.c
@@ -2690,10 +2690,11 @@ H5C__prep_for_file_close__setup_image_entries_array(H5C_t *cache_ptr)
              */
             if (entry_ptr->type->id == H5AC_PREFETCHED_ENTRY_ID) {
                 image_entries[u].type_id = entry_ptr->prefetch_type_id;
-                image_entries[u].age     = entry_ptr->age + 1;
 
-                if (image_entries[u].age > H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX)
+                if (entry_ptr->age >= H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX)
                     image_entries[u].age = H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX;
+                else
+                    image_entries[u].age = entry_ptr->age + 1;
             } /* end if */
             else {
                 image_entries[u].type_id = entry_ptr->type->id;