Re:cygwin, libtool, dlpreopen, and .rdata

[Ralf Habacker <ralf dot habacker at freenet dot de>]

Hi Chuck, 

you wrote
>With newer gcc's (cygwin version numbers 3.3.3-3, 3.4.1-1, but not 3.3.1-3), 
>const variables are placed in an .rdata section. This causes problems when 
>those  variables contain references to OTHER vars that are imported from a 
dll -- because the runtime relocation machinery can't fixup the address, 
since the  variable holding the address is const -- and is in .rdata!
<snip>
>But it can't, because .rdata is non-writable. However, this is a *runtime* 
>error; the *link* succeeds. But when you run the app, you get a popup window 
>declaring:
>
>"The application failed to initialize properly (0xc0000005). Click on OK to 
>terminate the application."
>
>Note that (1) the "nothing" relocation works fine for "normal" links; 
hell.exe  works ok, and imports "nothing" correctly.
>
<snip>
>************************************* 
>I see two solutions: a short term libtool->focused workaround, 
>and a longer term general solution. 
>
stumpled the last time about this problem with qt/cygwin releases and found a 
generic workaround by using a specific linker script, which avoids rdata 
sections. (script is appended). 
Copy the linker script for example to /usr/lib/ldscripts and run the following 
line to link a dll. 

gcc -Wl,--script,/usr/lib/ldscripts/i386pe.x-no-rdata 


May be this help some people 

Regards 
Ralf 




/* specific linker script avoiding .rdata sections, for normal executables 
for a reference see 
http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
http://www.cygwin.com/ml/cygwin-apps/2004-09/msg00309.html
*/
OUTPUT_FORMAT(pei-i386)
SEARCH_DIR("/usr/i686-pc-cygwin/lib"); SEARCH_DIR("/usr/lib"); SEARCH_DIR("/usr/lib/w32api");
ENTRY(_mainCRTStartup)
SECTIONS
{
  .text  __image_base__ + __section_alignment__  :
  {
     *(.init)
    *(.text)
    *(SORT(.text$*))
    *(.glue_7t)
    *(.glue_7)
     ___CTOR_LIST__ = .; __CTOR_LIST__ = . ;
			LONG (-1);*(.ctors); *(.ctor); *(SORT(.ctors.*));  LONG (0);
     ___DTOR_LIST__ = .; __DTOR_LIST__ = . ;
			LONG (-1); *(.dtors); *(.dtor); *(SORT(.dtors.*));  LONG (0);
     *(.fini)
    /* ??? Why is .gcc_exc here?  */
     *(.gcc_exc)
    PROVIDE (etext = .);
    *(.gcc_except_table)
  }
  /* The Cygwin32 library uses a section to avoid copying certain data
     on fork.  This used to be named ".data".  The linker used
     to include this between __data_start__ and __data_end__, but that
     breaks building the cygwin32 dll.  Instead, we name the section
     ".data_cygwin_nocopy" and explictly include it after __data_end__. */
  .data BLOCK(__section_alignment__) :
  {
    __data_start__ = . ;
    *(.data)
    *(.data2)
    *(SORT(.data$*))
    *(.rdata)
    *(SORT(.rdata$*))
    *(.eh_frame)
    ___RUNTIME_PSEUDO_RELOC_LIST__ = .;
    __RUNTIME_PSEUDO_RELOC_LIST__ = .;
    *(.rdata_runtime_pseudo_reloc)
    ___RUNTIME_PSEUDO_RELOC_LIST_END__ = .;
    __RUNTIME_PSEUDO_RELOC_LIST_END__ = .;
    __data_end__ = . ;
    *(.data_cygwin_nocopy)
  }
  .rdata BLOCK(__section_alignment__) :
  {
  }
  .pdata BLOCK(__section_alignment__) :
  {
    *(.pdata)
  }
  .bss BLOCK(__section_alignment__) :
  {
    __bss_start__ = . ;
    *(.bss)
    *(COMMON)
    __bss_end__ = . ;
  }
  .edata BLOCK(__section_alignment__) :
  {
    *(.edata)
  }
  /DISCARD/ :
  {
    *(.debug$S)
    *(.debug$T)
    *(.debug$F)
    *(.drectve)
  }
  .idata BLOCK(__section_alignment__) :
  {
    /* This cannot currently be handled with grouped sections.
	See pe.em:sort_sections.  */
    SORT(*)(.idata$2)
    SORT(*)(.idata$3)
    /* These zeroes mark the end of the import list.  */
    LONG (0); LONG (0); LONG (0); LONG (0); LONG (0);
    SORT(*)(.idata$4)
    SORT(*)(.idata$5)
    SORT(*)(.idata$6)
    SORT(*)(.idata$7)
  }
  .CRT BLOCK(__section_alignment__) :
  {
    ___crt_xc_start__ = . ;
    *(SORT(.CRT$XC*))  /* C initialization */
    ___crt_xc_end__ = . ;
    ___crt_xi_start__ = . ;
    *(SORT(.CRT$XI*))  /* C++ initialization */
    ___crt_xi_end__ = . ;
    ___crt_xl_start__ = . ;
    *(SORT(.CRT$XL*))  /* TLS callbacks */
    /* ___crt_xl_end__ is defined in the TLS Directory support code */
    ___crt_xp_start__ = . ;
    *(SORT(.CRT$XP*))  /* Pre-termination */
    ___crt_xp_end__ = . ;
    ___crt_xt_start__ = . ;
    *(SORT(.CRT$XT*))  /* Termination */
    ___crt_xt_end__ = . ;
  }
  .tls BLOCK(__section_alignment__) :
  {
    ___tls_start__ = . ;
    *(.tls)
    *(.tls$)
    *(SORT(.tls$*))
    ___tls_end__ = . ;
  }
  .endjunk BLOCK(__section_alignment__) :
  {
    /* end is deprecated, don't use it */
    PROVIDE (end = .);
    PROVIDE ( _end = .);
     __end__ = .;
  }
  .rsrc BLOCK(__section_alignment__) :
  {
    *(.rsrc)
    *(SORT(.rsrc$*))
  }
  .reloc BLOCK(__section_alignment__) :
  {
    *(.reloc)
  }
  .stab BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.stab)
  }
  .stabstr BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.stabstr)
  }
  /* DWARF debug sections.
     Symbols in the DWARF debugging sections are relative to the beginning
     of the section.  Unlike other targets that fake this by putting the
     section VMA at 0, the PE format will not allow it.  */
  /* DWARF 1.1 and DWARF 2.  */
  .debug_aranges BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_aranges)
  }
  .debug_pubnames BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_pubnames)
  }
  /* DWARF 2.  */
  .debug_info BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_info) *(.gnu.linkonce.wi.*)
  }
  .debug_abbrev BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_abbrev)
  }
  .debug_line BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_line)
  }
  .debug_frame BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_frame)
  }
  .debug_str BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_str)
  }
  .debug_loc BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_loc)
  }
  .debug_macinfo BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_macinfo)
  }
  /* SGI/MIPS DWARF 2 extensions.  */
  .debug_weaknames BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_weaknames)
  }
  .debug_funcnames BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_funcnames)
  }
  .debug_typenames BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_typenames)
  }
  .debug_varnames BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_varnames)
  }
  /* DWARF 3.  */
  .debug_ranges BLOCK(__section_alignment__) (NOLOAD) :
  {
    *(.debug_ranges)
  }
}

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