Remove H5_NO_ALIGNMENT_RESTRICTIONS (#1426)

* Do not conditionally compile code that uses a pointer dereference
and assignment to copy a potentially unaligned variable to aligned
automatic storage, or vice versa.  Instead, always use naked `memcpy(3)`s.
Disassembling the generated code reveals that the `memcpy(3)`s optimize
(`-O3`) to a single `mov` instruction for x86_64, which is not strict
about alignment.

This change reduces the size of code and scripts by 143 lines, eases
our way to cross-compilation, and avoids invoking undefined behavior.

* Committing clang-format changes

* Per discussion, use HD and add comments.

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

3 files changed, 0 insertions, 60 deletions

diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index 43aa243..9c91d34 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -416,7 +416,3 @@ H5ConversionTests (${HDF_PREFIX}_LLONG_TO_LDOUBLE_CORRECT "Checking IF correctly
 # some long double values
 #-----------------------------------------------------------------------------
 H5ConversionTests (${HDF_PREFIX}_DISABLE_SOME_LDOUBLE_CONV "Checking IF the cpu is power9 and cannot correctly converting long double values")
-# ----------------------------------------------------------------------
-# Check if pointer alignments are enforced
-#-----------------------------------------------------------------------------
-H5ConversionTests (${HDF_PREFIX}_NO_ALIGNMENT_RESTRICTIONS "Checking IF alignment restrictions are strictly enforced")
diff --git a/config/cmake/ConversionTests.c b/config/cmake/ConversionTests.c
index f80959f..f100dd8 100644
--- a/config/cmake/ConversionTests.c
+++ b/config/cmake/ConversionTests.c
@@ -234,59 +234,6 @@ done:
 }
 #endif
 
-#ifdef H5_NO_ALIGNMENT_RESTRICTIONS_TEST
-
-#include <stdlib.h>
-#include <string.h>
-
-typedef struct {
-    size_t len;
-    void *p;
-} hvl_t;
-
-#ifdef FC_DUMMY_MAIN
-#ifndef FC_DUMMY_MAIN_EQ_F77
-#  ifdef __cplusplus
-extern "C"
-#  endif
-int FC_DUMMY_MAIN()
-{ return 1;}
-#endif
-#endif
-int HDF_NO_UBSAN
-main ()
-{
-
-    char *chp = "beefs";
-    char **chpp = malloc (2 * sizeof (char *));
-    char **chpp2;
-    hvl_t vl = { 12345, (void *) chp };
-    hvl_t *vlp;
-    hvl_t *vlp2;
-
-    memcpy ((void *) ((char *) chpp + 1), &chp, sizeof (char *));
-    chpp2 = (char **) ((char *) chpp + 1);
-    if (strcmp (*chpp2, chp)) {
-        free (chpp);
-        return 1;
-    }
-    free (chpp);
-
-    vlp = malloc (2 * sizeof (hvl_t));
-    memcpy ((void *) ((char *) vlp + 1), &vl, sizeof (hvl_t));
-    vlp2 = (hvl_t *) ((char *) vlp + 1);
-    if (vlp2->len != vl.len || vlp2->p != vl.p) {
-        free (vlp);
-        return 1;
-    }
-    free (vlp);
-
-  ;
-  return 0;
-}
-
-#endif
-
 #ifdef H5_DISABLE_SOME_LDOUBLE_CONV_TEST
 
 #include <stdio.h>
diff --git a/config/cmake/H5pubconf.h.in b/config/cmake/H5pubconf.h.in
index 4956c97..9a581cb 100644
--- a/config/cmake/H5pubconf.h.in
+++ b/config/cmake/H5pubconf.h.in
@@ -434,9 +434,6 @@
 /* Define to enable internal memory allocation sanity checking. */
 #cmakedefine H5_MEMORY_ALLOC_SANITY_CHECK @H5_MEMORY_ALLOC_SANITY_CHECK@
 
-/* Define if we can violate pointer alignment restrictions */
-#cmakedefine H5_NO_ALIGNMENT_RESTRICTIONS @H5_NO_ALIGNMENT_RESTRICTIONS@
-
 /* Define if deprecated public API symbols are disabled */
 #cmakedefine H5_NO_DEPRECATED_SYMBOLS @H5_NO_DEPRECATED_SYMBOLS@