[Bug c++/12943] New: array static-init failure under -fpic, -fPIC

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12943

           Summary: array static-init failure under -fpic, -fPIC
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ncm-nospam at cantrip dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i486-pc-linux-gnu
  GCC host triplet: i486-pc-linux-gnu
GCC target triplet: i486-pc-linux-gnu

  Static linker initialization fails to initialize struct members, 
    under hard-to-describe circumstances.  

  Specifically: in a static array initialization where array elements 
  are structs, and where some struct members are implicitly initialized
  to zero, certain struct members that are *explicitly* initialized get
  zero-initialized anyhow.

  To reproduce the failure, it appears that:
    o  "-fpic" or "-fPIC" is necessary (but we have failures w/o -fpic).
    o  letting the compiler implicitly zero-initialize at least 
         one struct member in all elements is necessary.
    o  a forward-reference to the initialized value is necessary (or a
         string literal).
    o  fewer than five array elements is necessary (but we have seen it
         with more).

  Under "-O0" the failure does not seem to occur.
  In gcc-3.0 the failure does not seem to occur.
  In gcc-3.4 snapshots the failure *does* still occur.

Environment:
System: Linux ipc 2.4.21-rc1-ac2 #3 SMP Mon Apr 28 18:55:42 EDT 2003 i686 unknown unknown GNU/Linux
Architecture: i686

	
host: i486-pc-linux-gnu
build: i486-pc-linux-gnu
target: i486-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared --with-system-zlib --enable-nls --without-included-gettext --enable-__cxa_atexit --enable-clocale=gnu --enable-debug --enable-java-gc=boehm --enable-java-awt=xlib --enable-objc-gc i486-linux

How-To-Repeat:

  Paste lines below into a shell.  Correct output is 
    1 This is a message
    2 This is a message
  Erroneous output looks like
    1 This is a message
    2 <NULL>

  ----------------
  sed 's/^  //' >initbug.cc  <<'  EOF'
  // Compile this with 'g++ -O1 -fpic', and see what happens 
  // compiled as C, the problem does not occur.

  #include <stdio.h>

  struct StringHolder {
      int m_index;
      char const * const message_pointer;
      int extra;        //  this member is necessary to expose bug
  };

  extern char const * const Message;
  
  StringHolder array_of_holders[] = {
      { 1, Message },   // default-initializing Stringholder::extra
      { 2, Message },
      { -1, 0 }
  };
  
  int main()
  {
      StringHolder* ptr = array_of_holders;
      while(ptr->m_index >= 0) {
          printf("%d\t", ptr->m_index);
          if (ptr->message_pointer == NULL)
              printf("<NULL>\n");
          else
              printf("%s\n", ptr->message_pointer);
          ++ptr;
      }
  }
  char const * const Message = "This is a message";
  EOF
  g++ -O1 -fpic initbug.cc
  ./a.out