binutils-gdb/gdb/testsuite/gdb.arch/amd64-tailcall-self.c

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PR symtab/18392 Initially there is some chain (let's say the longest one but that doe snot matter). Consequently its elements from the middle are being removed and there remains only some few unambiguous top and bottom ones. The original idea why the comparison should be sharp ("<") was that if there are multiple chains like (0xaddr show jmp instruction address): main(0x100) -> a(0x200) -> d(0x400) main(0x100) -> a(0x200) -> c(0x300) -> d(0x400) then - such situation cannot exist - if two jmp instructions in "a" have the same address they must also jump to the same address (*). (*) jump to a computed address would be never considered for the DWARF tail-call records. So there could be: main(0x100) -> a(0x200) -> d(0x400) main(0x100) -> a(0x270) -> c(0x300) -> d(0x400) But then "a" frame itself is ambiguous and it must not be displayed. I did not realize that there can be self-tail-call: main(0x100) -> a(0x200) -> d(0x400) main(0x100) -> a(0x280) -> a(0x200) -> d(0x400) which intersects to: main(0x100) -> <???>? -> a(0x200) -> d(0x400) And so if the first chain was chosen the main(0x100) -> a(0x200) -> d(0x400) then the final intersection has callers+callees==length. > for example, if CALLERS is 3 and > CALLEES is 2, what does the chain look like? main(0x100) -> x(0x150) -> y(0x200) -> <???>? -> a(0x200) -> d(0x400) And if LENGTH is 7 then: call_site[0] = main(0x100) call_site[1] = x(0x150) call_site[2] = y(0x200) call_site[3] = garbage call_site[4] = garbage call_site[5] = a(0x200) call_site[6] = d(0x400) gdb/ChangeLog 2015-06-01 Andreas Schwab <schwab@linux-m68k.org> Jan Kratochvil <jan.kratochvil@redhat.com> PR symtab/18392 * dwarf2-frame-tailcall.c (pretended_chain_levels): Correct assertion. * dwarf2loc.c (chain_candidate): Likewise. gdb/testsuite/ChangeLog 2015-06-01 Jan Kratochvil <jan.kratochvil@redhat.com> PR symtab/18392 * gdb.arch/amd64-tailcall-self.S: New file. * gdb.arch/amd64-tailcall-self.c: New file. * gdb.arch/amd64-tailcall-self.exp: New file.
2015-06-01 20:02:34 +08:00
/* This testcase is part of GDB, the GNU debugger.
Copyright 2015 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
__attribute__((noinline,noclone)) static void b(void) {
asm volatile("");
}
int i;
__attribute__((noinline,noclone)) int c(int q) {
return q+1;
}
__attribute__((noinline,noclone)) void a(int q) {
asm volatile("nop;nop;nop"::"g"(q):"memory");
if (i>=1&&i<=10) {
i|=1;
a(i);
} else if (i==0)
b();
}
int main(int argc,char **argv) {
a(argc);
return 0;
}