[lldb-dev] breakpoint command

Michael Sartain mikesart at valvesoftware.com
Thu Jun 20 17:47:42 PDT 2013

On Wed, Jun 19, 2013 at 2:49 PM, Michael Sartain <mikesart at valvesoftware.com
> wrote:

> So I think the change would be in how lldb handles what the second line
> table entry is? Ie, skip duplicate entries.

I've added to this patch:


Modified Symbol::GetPrologueByteSize() in source/Symbol/Symbol.cpp and
Function::GetPrologueByteSize() in source/Symbol/Function.cpp. They should
both now skip line entries until they find a line number that differs.

One question: would it make sense to have Symbol::GetPrologueByteSize()
check to see if it is an exact alias to a function and if so, use the
Function::GetPrologueByteSize() routine? That way we'd get the prologue end
data instead of just skipping lines?

In any case, breakpoint setting in the printf case works as it should now:

(lldb) b printf
Breakpoint 2: where = libc.so.6`__printf + 91 at printf.c:34, address =
(lldb) b __printf
Breakpoint 3: where = libc.so.6`__printf + 91 at printf.c:34, address =
(lldb) b _IO_printf
Breakpoint 4: where = libc.so.6`__printf + 91 at printf.c:34, address =
(lldb) disassemble -n printf
libc.so.6`__printf at printf.c:30:
   0x7f8dba8b1840:  subq   $216, %rsp

libc.so.6`__printf + 7 at printf.c:30:
   0x7f8dba8b1847:  testb  %al, %al
   0x7f8dba8b1849:  movq   %rsi, 40(%rsp)
   0x7f8dba8b184e:  movq   %rdx, 48(%rsp)
   0x7f8dba8b1853:  movq   %rcx, 56(%rsp)
   0x7f8dba8b1858:  movq   %r8, 64(%rsp)
   0x7f8dba8b185d:  movq   %r9, 72(%rsp)
   0x7f8dba8b1862:  je     0x7f8dba8b189b            ; __printf + 91 at
   0x7f8dba8b1864:  movaps %xmm0, 80(%rsp)
   0x7f8dba8b1869:  movaps %xmm1, 96(%rsp)
   0x7f8dba8b186e:  movaps %xmm2, 112(%rsp)
   0x7f8dba8b1873:  movaps %xmm3, 128(%rsp)
   0x7f8dba8b187b:  movaps %xmm4, 144(%rsp)
   0x7f8dba8b1883:  movaps %xmm5, 160(%rsp)
   0x7f8dba8b188b:  movaps %xmm6, 176(%rsp)
   0x7f8dba8b1893:  movaps %xmm7, 192(%rsp)
   0x7f8dba8b189b:  leaq   224(%rsp), %rax
   0x7f8dba8b18a3:  movq   %rdi, %rsi
   0x7f8dba8b18a6:  leaq   8(%rsp), %rdx
   0x7f8dba8b18ab:  movl   $8, 8(%rsp)
   0x7f8dba8b18b3:  movl   $48, 12(%rsp)
   0x7f8dba8b18bb:  movq   %rax, 16(%rsp)
   0x7f8dba8b18c0:  leaq   32(%rsp), %rax
   0x7f8dba8b18c5:  movq   %rax, 24(%rsp)
   0x7f8dba8b18ca:  movq   3556935(%rip), %rax
   0x7f8dba8b18d1:  movq   (%rax), %rdi
   0x7f8dba8b18d4:  callq  0x7f8dba8a69c0            ;
_IO_vfprintf_internal at vfprintf.c:211
   0x7f8dba8b18d9:  addq   $216, %rsp
   0x7f8dba8b18e0:  ret

I'd love to hear feedback on this patch and the split symbol patch overall.
I've built it on the Mac using cmake & ninja (won't run locally without
debugserver though?). I'm still having issues with xcodebuild randomly
failing to link on my Mac, and it seems to rebuild the whole thing when I
launch xcodebuild again which takes forever. (This Mac thing has been
pretty frustrating.) I've run the entire test suite on Linux, and it says
there are some new failure cases but when I run them individually (not
through ninja check-lldb) they work. So I'm finding it a bit difficult to
verify all this stuff. I'm also gone all next week, so if folks are worried
about this large patch it might make sense to wait until early July. I
would like to get it looked over and in at some point because the merging
is becoming more painful.

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