Linking C++

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

There is a restriction in our ld.elf_so that it can only load two
segments.

Using devel/lld to link C++ objects on aarch64 creats a shlib with three
segments that then fails to load.

On aarch64 .init_array contains static constructors, on x86_64 they
are in .ctors.

What is expected to happen to delete or combine segments in a linker
to get down to two of them ? Hints on where to look in gcc or binutils
would be good.

An example on aarch64:

% readelf -l libjvm.so

Elf file type is DYN (Shared object file)
Entry point 0x3dbd40
There are 10 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  PHDR           0x0000000000000040 0x0000000000000040 0x0000000000000040
                 0x0000000000000230 0x0000000000000230  R      0x8
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000c7ca70 0x0000000000c7ca70  R E    0x10000
  LOAD           0x0000000000c80000 0x0000000000c80000 0x0000000000c80000
                 0x0000000000095348 0x0000000000095348  RW     0x10000
  LOAD           0x0000000000d20000 0x0000000000d20000 0x0000000000d20000
                 0x000000000002e270 0x000000000009cd40  RW     0x10000
  TLS            0x0000000000c7ca70 0x0000000000c7ca70 0x0000000000c7ca70
                 0x0000000000000000 0x0000000000000028  R      0x8
  DYNAMIC        0x0000000000d0d290 0x0000000000d0d290 0x0000000000d0d290
                 0x00000000000001d0 0x00000000000001d0  RW     0x8
  GNU_RELRO      0x0000000000c80000 0x0000000000c80000 0x0000000000c80000
                 0x0000000000095348 0x0000000000096000  R      0x1
  GNU_EH_FRAME   0x000000000027d2a0 0x000000000027d2a0 0x000000000027d2a0
                 0x000000000004864c 0x000000000004864c  R      0x4
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RW     0x0
  NOTE           0x0000000000000270 0x0000000000000270 0x0000000000000270
                 0x000000000000002c 0x000000000000002c  R      0x4

 Section to Segment mapping:
  Segment Sections...
   00     
   01     .note.netbsd.ident .note.netbsd.pax .dynsym .gnu.version .gnu.version_d .gnu.version_r .gnu.hash .hash .dynstr .rela.dyn .rela.plt .rodata .eh_frame_hdr .eh_frame .text .plt 
   02     .init_array .fini_array .jcr .data.rel.ro .dynamic .got 
   03     .data .got.plt .bss 
   04     .tbss 
   05     .dynamic 
   06     .init_array .fini_array .jcr .data.rel.ro .dynamic .got 
   07     .eh_frame_hdr 
   08     
   09     .note.netbsd.ident .note.netbsd.pax 


The equivalent x86_64 shlib shows this:

% readelf -l libjvm.so

Elf file type is DYN (Shared object file)
Entry point 0x2683a0
There are 9 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  PHDR           0x0000000000000040 0x0000000000000040 0x0000000000000040
                 0x00000000000001f8 0x00000000000001f8  R      0x8
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000001002928 0x0000000001002928  R E    0x200000
  LOAD           0x0000000001002fb8 0x0000000001202fb8 0x0000000001202fb8
                 0x00000000000f3520 0x0000000000143100  RW     0x200000
  DYNAMIC        0x00000000010bdc90 0x00000000012bdc90 0x00000000012bdc90
                 0x00000000000001f0 0x00000000000001f0  RW     0x8
  NOTE           0x00000000010028fc 0x00000000010028fc 0x00000000010028fc
                 0x000000000000002c 0x000000000000002c  R      0x4
  TLS            0x0000000001002fb8 0x0000000001202fb8 0x0000000001202fb8
                 0x0000000000000000 0x0000000000000008  R      0x8
  GNU_EH_FRAME   0x0000000000e4933c 0x0000000000e4933c 0x0000000000e4933c
                 0x000000000004b234 0x000000000004b234  R      0x4
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RW     0x10
  GNU_RELRO      0x0000000001002fb8 0x0000000001202fb8 0x0000000001202fb8
                 0x00000000000bb048 0x00000000000bb048  R      0x1

 Section to Segment mapping:
  Segment Sections...
   00     
   01     .hash .dynsym .dynstr .gnu.version .gnu.version_d .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini .rodata .eh_frame_hdr .eh_frame .note.netbsd.ident .note.netbsd.pax 
   02     .ctors .dtors .jcr .data.rel.ro .dynamic .got .got.plt .data .bss 
   03     .dynamic 
   04     .note.netbsd.ident .note.netbsd.pax 
   05     .tbss 
   06     .eh_frame_hdr 
   07     
   08     .ctors .dtors .jcr .data.rel.ro .dynamic .got