Based on DWARF2 Standard (6.4.2 Call Frame Instructions), The instructions "DW_CFA_undefined" & "DW_CFA_same_value" takes a single unsigned LEB128 argument that represents a register number. While executing these instructions, The runtime library is not treating the next data as operands to the "DW_CFA_undefined" & "DW_CFA_same_value" instructions. Instead, it treats them as opcodes and executes them. Due to this, the program behaviour changes and gives segmentation fault at runtime. This is not a problem when I use gcc compiler and libraries. Because, gcc compiler may not be generating "DW_CFA_undefined" & "DW_CFA_same_value" instructions. But, This is an interoperability issue. I tried to compile the testcase with intel compiler and linked with gcc libraries. I got segmentation fault. Fix for this problem may be simple. While handling "DW_CFA_undefined" & "DW_CFA_same_value" instructions (in file: gcc-3.2/gcc/unwind-dw2.c, function: execute_cfa_program), read the next LEB128 argument and ignore it. Please let me know, if it is not correct. Thanks, -Sunil. Release: gcc-3.2 Environment: $ g++ -v Reading specs from /local/skdavasa/gcc321/lib/gcc-lib/i386-redhat-linux/3.2.1/specs Configured with: gcc-3.2.1/configure --prefix=/local/skdavasa/gcc321 --enable-shared --enable-threads=posix --disable-checking --host=i386-redhat-linux --with-system-zlib --enable-__cxa_atexit Thread model: posix gcc version 3.2.1 cat /etc/issue Red Hat Linux release 8.0 (Psyche) Kernel \r on an \m
Fix: file: gcc-3.2/gcc/unwind-dw2.c function: execute_cfa_program code: static void execute_cfa_program (const unsigned char *insn_ptr, const unsigned char *insn_end, struct _Unwind_Context *context, _Unwind_FrameState *fs) { .... .... switch (insn) { case DW_CFA_set_loc: insn_ptr = read_encoded_value (context, fs->fde_encoding, insn_ptr, (_Unwind_Ptr *) &fs->pc); break; case DW_CFA_advance_loc1: fs->pc += read_1u (insn_ptr) * fs->code_align; insn_ptr += 1; break; case DW_CFA_advance_loc2: fs->pc += read_2u (insn_ptr) * fs->code_align; insn_ptr += 2; break; case DW_CFA_advance_loc4: fs->pc += read_4u (insn_ptr) * fs->code_align; insn_ptr += 4; break; case DW_CFA_offset_extended: insn_ptr = read_uleb128 (insn_ptr, ®); insn_ptr = read_uleb128 (insn_ptr, &utmp); offset = (_Unwind_Sword) utmp * fs->data_align; fs->regs.reg[reg].how = REG_SAVED_OFFSET; fs->regs.reg[reg].loc.offset = offset; break; case DW_CFA_restore_extended: insn_ptr = read_uleb128 (insn_ptr, ®); fs->regs.reg[reg].how = REG_UNSAVED; break; 770 case DW_CFA_undefined: 771 case DW_CFA_same_value: 772 case DW_CFA_nop: 773 break; ..... ..... } Change the code in line numbers from 770 to 773 to the following.. case DW_CFA_undefined: case DW_CFA_same_value: insn_ptr = read_uleb128 (insn_ptr, ®); break; case DW_CFA_nop: break; ........
Responsible-Changed-From-To: unassigned->rth Responsible-Changed-Why: Hey Richard can you give me some feedback about this? This bug has a patch enclosed to unwind-dw2.c, and it seems reasonable. Thanks, benjamin
State-Changed-From-To: open->analyzed State-Changed-Why: Seems reasonable.
Responsible-Changed-From-To: rth->bkoz Responsible-Changed-Why: Ok, well whatever.
State-Changed-From-To: analyzed->closed State-Changed-Why: In gcc, gcc-3_3-branch, gcc-3_3-branch.
From: bkoz@gcc.gnu.org To: gcc-gnats@gcc.gnu.org Cc: Subject: libstdc++/9076 Date: 7 Jan 2003 20:20:54 -0000 CVSROOT: /cvs/gcc Module name: gcc Changes by: bkoz@gcc.gnu.org 2003-01-07 12:20:54 Modified files: gcc : ChangeLog unwind-dw2.c Log message: 2003-01-07 Benjamin Kosnik <bkoz@redhat.com> Sunil Davasam <sunil.k.davasam@intel.com> PR libstdc++/9076 * unwind-dw2.c (execute_cfa_program): DW_CFA_undefined, DW_CFA_same_value, read next and ignore. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=1.16276&r2=1.16277 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/unwind-dw2.c.diff?cvsroot=gcc&r1=1.23&r2=1.24
From: bkoz@gcc.gnu.org To: gcc-gnats@gcc.gnu.org Cc: Subject: libstdc++/9076 Date: 7 Jan 2003 20:33:05 -0000 CVSROOT: /cvs/gcc Module name: gcc Branch: gcc-3_3-branch Changes by: bkoz@gcc.gnu.org 2003-01-07 12:33:05 Modified files: gcc : ChangeLog unwind-dw2.c Log message: 2003-01-07 Benjamin Kosnik <bkoz@redhat.com> Sunil Davasam <sunil.k.davasam@intel.com> PR libstdc++/9076 * unwind-dw2.c (execute_cfa_program): DW_CFA_undefined, DW_CFA_same_value, read next and ignore. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.16114.2.40&r2=1.16114.2.41 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/unwind-dw2.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.22&r2=1.22.2.1
From: bkoz@gcc.gnu.org To: gcc-gnats@gcc.gnu.org Cc: Subject: libstdc++/9076 Date: 7 Jan 2003 20:36:19 -0000 CVSROOT: /cvs/gcc Module name: gcc Branch: gcc-3_2-branch Changes by: bkoz@gcc.gnu.org 2003-01-07 12:36:19 Modified files: gcc : unwind-dw2.c ChangeLog Log message: 2003-01-07 Benjamin Kosnik <bkoz@redhat.com> Sunil Davasam <sunil.k.davasam@intel.com> PR libstdc++/9076 * unwind-dw2.c (execute_cfa_program): DW_CFA_undefined, DW_CFA_same_value, read next and ignore. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/unwind-dw2.c.diff?cvsroot=gcc&only_with_tag=gcc-3_2-branch&r1=1.18&r2=1.18.6.1 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_2-branch&r1=1.13152.2.657.2.170&r2=1.13152.2.657.2.171
*** Bug 8540 has been marked as a duplicate of this bug. ***