From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mumit Khan <khan@xraylith.wisc.edu>
To: gas2@cygnus.com
Subject: i386-pe named linkonce section switching problem
Date: Wed, 02 Sep 1998 08:56:00 -0000
Message-id: <9809021556.AA06709@modi.xraylith.wisc.edu>
X-SW-Source: 1998/msg00214.html

Platform : i386-pe (mingw32, cygwin32, etc)
binutils : everything upto and including 980830
compiler : egcs-1.1

The following C++ code shows an odd problem with switching named linkonce
sections within the same object file, and such code shows up in C++ with 
jump tables. Essentially, we lose the linkonce directive after the switch.

If you compile the following without optimization (ie., no inlining), then
in the assembly output of 'func(char)', the compiler generates the initial
code in section	'.text$func__Fc' marked linkonce; then it switches to
.text (we're not using .rdata for x86-win32 yet) for the jump table and
switches back to .text$func__Fc for the rest. In the process of switching
back, the linkonce is lost and the linker finds multiple definitions if
the inline function is included elsewere as well.

If I add a ``.linkonce discard'' to the second .section .text$func__Fc
when it switches back, the linkonce is preserved, but the final executable 
crashes.

Any ideas on a fix?

Regards,
Mumit

======================= bug.cc ==========================
  inline
  int func(char c)
  {
    switch (c)
      {
      case 'a':return 1;
      case 't':return 2;
      case 'g':return 3;
      case 'c':return 4;
      case 'n':return 5;
      }
  }

  int func2(char c) { return func(c); }

======================= build ==========================

% i386-mingw32-gcc bug.cc

============== nm output ===========================================

bug.o:     file format pe-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00000080  00000000  00000000  000000b4  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, CODE
  1 .data         00000000  00000000  00000000  00000000  2**2
                  ALLOC, LOAD, DATA
  2 .bss          00000000  00000000  00000000  00000000  2**2
                  ALLOC
  3 .text$func__Fc 00000060  00000000  00000000  00000134  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, CODE

======================= bug.s ==========================

	.file	"bug.cc"
gcc2_compiled.:
___gnu_compiled_cplusplus:
.text
	.align 4
.globl _func2__Fc
	.def	_func2__Fc;	.scl	2;	.type	32;	.endef
_func2__Fc:
	pushl %ebp
	movl %esp,%ebp
	subl $16,%esp
	movl 8(%ebp),%eax
	movb %al,-1(%ebp)
	movsbl -1(%ebp),%eax
	pushl %eax
	call _func__Fc
	addl $4,%esp
	movl %eax,%edx
	movl %edx,%eax
	jmp L11
	jmp L12
	jmp L11
	.p2align 4,,7
L12:
L11:
	leave
	ret
.section	.text$func__Fc,"x"
	.linkonce discard
	.align 4
.globl _func__Fc
	.def	_func__Fc;	.scl	2;	.type	32;	.endef
_func__Fc:
	pushl %ebp
	movl %esp,%ebp
	movl 8(%ebp),%eax
	movb %al,%dl
	movb %dl,%cl
	addb $-97,%cl
	movsbl %cl,%eax
	cmpl $19,%eax
	ja L2
	movl L8(,%eax,4),%eax
	jmp *%eax
	.p2align 4,,7
.text
L8:
	.long L3
	.long L2
	.long L6
	.long L2
	.long L2
	.long L2
	.long L5
	.long L2
	.long L2
	.long L2
	.long L2
	.long L2
	.long L2
	.long L7
	.long L2
	.long L2
	.long L2
	.long L2
	.long L2
	.long L4
.section	.text$func__Fc,"x"
	.p2align 4,,7
L3:
	movl $1,%eax
	jmp L1
	.p2align 4,,7
L4:
	movl $2,%eax
	jmp L1
	.p2align 4,,7
L5:
	movl $3,%eax
	jmp L1
	.p2align 4,,7
L6:
	movl $4,%eax
	jmp L1
	.p2align 4,,7
L7:
	movl $5,%eax
	jmp L1
	.p2align 4,,7
L9:
L2:
	jmp L10
	jmp L1
	.p2align 4,,7
L10:
L1:
	leave
	ret
	.def	_func__Fc;	.scl	2;	.type	32;	.endef

=======================================================================