Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-37788

fix uintNkorr in byte_order_generic.h, avoid unaligned access

    XMLWordPrintable

Details

    • Can result in hang or crash
    • avoid unaligned access on Intel processors, which can result in unexpected crashes, when built with newer GCC.

    Description

      Compilers are getting (too) smart, and they can generate incorrect code, for unaligned access, since it is "undefined behavior".

      Also, avoid macros, like MySQL did, it is almost impossible to read now. `static inline` is good enough, and documents correct datatype
      of the return value.

      • the correct optimization for all little endian is something like this.

      static inline uint uint4korr(const void *p)
      		 
      {
      		 
        uint ret;
      		 
        memcpy(&ret, p, 4);
      		 
        return ret;
      		 
      }

      It is optimized by the compiler to a single instruction, if alignment is unimportant in that architecture.
      Corollary : There is no whatever reason to have special code for Intel, memcpy is the best.
      We only need set of such static inline functions for big and little endian architectures, nothing more.

      For big-endian, byte-wise reading and calculating are in order. That code might also by optimized by the compiler, if architecture has a byteswapping instructions.

      Attachments

        Issue Links

          blocks

          Bug - A problem which impairs or prevents the functions of the product. MDEV-39027 suboptimal code for InnoDB big endian access functions (MSVC, GCC)

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-39150 Some data conversion macros fail to use memcpy()

          • Major - Major loss of function.
          • Open
          relates to

          Task - A task that needs to be done. MDEV-20277 Disable -fno-strict-aliasing

          • Major - Major loss of function.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. MDEV-37148 Unaligned access in strings/ctype.c, crashes with upcoming GCC 16 (or UBSAN)

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-37786 my_convert randomly crashes when converting from utf8mb3 to utf8mb4

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-38989 main.ctype_utf16le SEGV in Ubuntu 26.04 (amd64v3)

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-37717 UBSAN: runtime error: store to misaligned address for type 'uint32' (aka 'unsigned int'), which requires 4 byte alignment in extra/comp_err

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-38398 SEGV on amd64v3 instruction set in my_convert

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Activity

            People

              wlad Vladislav Vaintroub
              wlad Vladislav Vaintroub
              Vladislav Vaintroub Vladislav Vaintroub
              Votes:
              1 Vote for this issue
              Watchers:
              6 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved:

                Git Integration

                  Error rendering 'com.xiplink.jira.git.jira_git_plugin:git-issue-webpanel'. Please contact your Jira administrators.