Align checksum page error list in manifest file packs.

This was left unaligned on purpose to save space but the sanitizer did not like it. Since this field is seldom used go ahead and align it to make the sanitizer happy.

Also add some macros to make working with alignment easier.

Found with -fsanitize=undefined.

src/common/macro.h

@@ -85,4 +85,18 @@ Adapted from PostgreSQL src/include/c.h.
         ((type)(expression))
 #endif
 
+/***********************************************************************************************************************************
+Determine the alignment of a data type
+
+This macro reduces to a constant so it is safe to use anywhere a constant is allowed, e.g. a switch statement case.
+***********************************************************************************************************************************/
+#define ALIGN_OF(type) ((size_t)&((struct {char c; type t;} *)0)->t)
+
+/***********************************************************************************************************************************
+Determine the byte offset required to align a type after an arbitrary number of bytes
+
+This is useful for determining how to correctly align a type in a buffer that is being dynamically built up like a struct.
+***********************************************************************************************************************************/
+#define ALIGN_OFFSET(type, bytes) (ALIGN_OF(type) - ((bytes) % ALIGN_OF(type)))
+
 #endif

src/info/manifest.c

@@ -315,24 +315,26 @@ manifestFilePack(const Manifest *const manifest, const ManifestFile *const file)
     }
 
     // Allocate memory for the file pack
+    const size_t nameSize = strSize(file->name) + 1;
+
     uint8_t *const result = memNew(
-        sizeof(StringPub) + strSize(file->name) + 1 + bufferPos + (file->checksumPageErrorList != NULL ?
-            sizeof(StringPub) + strSize(file->checksumPageErrorList) + 1 : 0));
+        sizeof(StringPub) + nameSize + bufferPos + (file->checksumPageErrorList != NULL ?
+            ALIGN_OFFSET(StringPub, nameSize + bufferPos) + sizeof(StringPub) + strSize(file->checksumPageErrorList) + 1 : 0));
 
     // Create string object for the file name
     *(StringPub *)result = (StringPub){.size = (unsigned int)strSize(file->name), .buffer = (char *)result + sizeof(StringPub)};
     size_t resultPos = sizeof(StringPub);
 
-    memcpy(result + resultPos, (uint8_t *)strZ(file->name), strSize(file->name) + 1);
-    resultPos += strSize(file->name) + 1;
+    memcpy(result + resultPos, (uint8_t *)strZ(file->name), nameSize);
+    resultPos += nameSize;
 
     // Copy pack data
     memcpy(result + resultPos, buffer, bufferPos);
 
     // Create string object for the checksum error list
     if (file->checksumPageErrorList != NULL)
     {
-        resultPos += bufferPos;
+        resultPos += bufferPos + ALIGN_OFFSET(StringPub, nameSize + bufferPos);
 
         *(StringPub *)(result + resultPos) = (StringPub)
             {.size = (unsigned int)strSize(file->checksumPageErrorList), .buffer = (char *)result + resultPos + sizeof(StringPub)};
@@ -414,7 +416,7 @@ manifestFileUnpack(const Manifest *const manifest, const ManifestFilePack *const
     result.checksumPageError = flag & (1 << manifestFilePackFlagChecksumPageError) ? true : false;
 
     if (flag & (1 << manifestFilePackFlagChecksumPageErrorList))
-        result.checksumPageErrorList = (const String *)((const uint8_t *)filePack + bufferPos);
+        result.checksumPageErrorList = (const String *)((const uint8_t *)filePack + bufferPos + ALIGN_OFFSET(StringPub, bufferPos));
 
     FUNCTION_TEST_RETURN(result);
 }