(original) (raw)

On Feb 17, 2020, at 12:25 PM, Levo DeLellis <levo.delellis@gmail.com> wrote:

It looks like I wasn't careful and mixed version. I compiled with clang-9 but used lldb-6\. Surprisingly this was the only error I notice when mixing these version. I could swear I tried compiling with clang-6\. I'd double check but it appears that installing lldb-9 removed lldb(-6) from my system

Thanks for pointing me in the right direction

On Mon, Feb 17, 2020 at 11:18 AM Adrian Prantl <aprantl@apple.com> wrote:

That is interesting. According to LLDB's test/lang/c/vla/\* frame variable for a VLA is supposed to work. Frame variable is also supposed to hide the \_\_vla\_expr0 artificial helper variable. Is this an older LLDB from your system or an LLDB you built from source? If yes, would you mind filing a bugreport about this?

thanks,
adrian

\> On Feb 15, 2020, at 8:17 AM, Levo DeLellis <levo.delellis@gmail.com> wrote:
\>
\> Thanks for the suggestions but it doesn't appear to be working correctly for me. I tried building the below after seeing the results with "clang -g -std=c99 test.c" and got the same result
\>
\> LLDB thinks MyArray is 81 elements long even though 81 and 80 doesn't show up anywhere in the llvm-ir (I tried again using an llvm ir file made by clang -g -std=c99 test.c -S -emit-llvm and clang -g test.ll)
\>
\> $ cat test.c
\> int foo(int s) {
\> int MyArray\[s\];
\> int i;
\> for (i = 0; i < s; ++i)
\> MyArray\[i\] = s;
\> return 0;
\> }
\>
\> int main(){
\> foo(5);
\> return 0;
\> }
\> $ clang -g test.c
\> $ lldb ./a.out
\> (lldb) target create "./a.out"
\> Current executable set to './a.out' (x86\_64).
\> (lldb) break set -f test.c -l 6
\> Breakpoint 1: where = a.out\`foo + 101 at test.c:7, address = 0x0000000000400505
\> (lldb) r
\> Process 3205 launched: './a.out' (x86\_64)
\> Process 3205 stopped
\> \* thread #1, name = 'a.out', stop reason = breakpoint 1.1
\> frame #0: 0x0000000000400505 a.out\`foo(s=5) at test.c:7
\> 4 for (i = 0; i < s; ++i)
\> 5 MyArray\[i\] = s;
\> 6 return 0;
\> -> 7 }
\> 8
\> 9 int main(){
\> 10 foo(5);
\> (lldb) frame variable
\> (int) s = 5
\> (unsigned long) \_\_vla\_expr0 = 5
\> (int) i = 5
\> (int \[81\]) MyArray = {
\> \[0\] = 5
\> \[1\] = 5
\> \[2\] = 5
\> \[3\] = 5
\> \[4\] = 5
\> \[5\] = 0
\> \[6\] = -136481184
\> \[7\] = 32767
\> \[8\] = -8408
\> \[9\] = 32767
\> \[10\] = -8544
\> \[11\] = 32767
\> \[12\] = 1
\> \[13\] = 5
\> \[14\] = 5
\> \[15\] = 0
\> \[16\] = -8512
\> \[17\] = 32767
\> \[18\] = 0
\> \[19\] = 5
\> \[20\] = -8432
\> \[21\] = 32767
\> \[22\] = 4195641
\> \[23\] = 0
\> \[24\] = -8208
\> \[25\] = 32767
\> \[26\] = 0
\> \[27\] = 0
\> \[28\] = 4195664
\> \[29\] = 0
\> \[30\] = -140485737
\> \[31\] = 32767
\> \[32\] = 0
\> \[33\] = 32
\> \[34\] = -8200
\> \[35\] = 32767
\> \[36\] = 0
\> \[37\] = 1
\> \[38\] = 4195616
\> \[39\] = 0
\> \[40\] = 0
\> \[41\] = 0
\> \[42\] = -1953144313
\> \[43\] = 1284291557
\> \[44\] = 4195248
\> \[45\] = 0
\> \[46\] = -8208
\> \[47\] = 32767
\> \[48\] = 0
\> \[49\] = 0
\> \[50\] = 0
\> \[51\] = 0
\> \[52\] = 1064657415
\> \[53\] = -1284291430
\> \[54\] = 933978631
\> \[55\] = -1284287451
\> \[56\] = 0
\> \[57\] = 32767
\> \[58\] = 0
\> \[59\] = 0
\> \[60\] = 0
\> \[61\] = 0
\> \[62\] = -136423629
\> \[63\] = 32767
\> \[64\] = -136530376
\> \[65\] = 32767
\> \[66\] = 386784
\> \[67\] = 0
\> \[68\] = 0
\> \[69\] = 0
\> \[70\] = 0
\> \[71\] = 0
\> \[72\] = 0
\> \[73\] = 0
\> \[74\] = 4195248
\> \[75\] = 0
\> \[76\] = -8208
\> \[77\] = 32767
\> \[78\] = 4195290
\> \[79\] = 0
\> \[80\] = -8216
\> }
\>
\>
\> On Thu, Feb 13, 2020 at 3:53 PM Adrian Prantl <aprantl@apple.com> wrote:
\> Take a look at the IR clang produces for C99 variable-length arrays.
\>
\> -- adrian
\>
\>> On Feb 13, 2020, at 10:03 AM, Levo DeLellis via llvm-dev <llvm-dev@lists.llvm.org> wrote:
\>>
\>> Hi. I searched and the closest thing I could find was this http://lists.llvm.org/pipermail/llvm-dev/2018-February/121348.html
\>>
\>> Currently a known sized array looks and debugs as expected. I use llvm.dbg.declare with DICompositeType tag: DW\_TAG\_array\_type and the size field. In my language arrays are always passed around with a pointer and size pair. I'd like debugging to show up as nicely instead of a pointer addr with no information about the elements. How would I do this? I don't use the C API, I output llvm-ir directly. I was hoping I can call llvm.dbg.declare/addr/value to specify the pointer, name and size of the variable but I really have no idea how to pass the size to the debugger.
\>>
\>> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
\>> LLVM Developers mailing list
\>> llvm-dev@lists.llvm.org
\>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
\>