LLDB hangs at O0

[YangYibiao]

$ clang --version

Ubuntu clang version 19.0.0 (++20240301064251+dd426fa5f931-1~exp1~20240301184412.1845) Target: x86_64-pc-linux-gnu Thread model: posix InstalledDir: /usr/lib/llvm-19/bin

$ lldb --version

lldb version 19.0.0

$ cat small.c

typedef struct { int baddr; } mstruct_t;

static struct { unsigned int mapnum; mstruct_t unused; } mtab;

static mstruct_t *mactab = &mtab.unused;

int main(void) { int i; int addr;

for (i=1; i <= mtab.mapnum; i++) if (addr < mactab[i].baddr) break; return 0; }

$ clang -O0 -g small.c; lldb a.out

(lldb) target create "a.out" Current executable set to '/root/a.out' (x86_64). (lldb) b main Breakpoint 1: where = a.out`main + 11 at small.c:20:9, address = 0x000000000000113b (lldb) r Process 26442 launched: '/root/a.out' (x86_64) [1344/3230] Manually indexing DWARF: libc.so.6...

The code you provided is causing LLDB to hang after setting a breakpoint at main and attempting to run the program.

[llvmbot]

@llvm/issue-subscribers-lldb

Author: Alex (HelloAlexy)

`$ clang --version` > Ubuntu clang version 19.0.0 (++20240301064251+dd426fa5f931-1~exp1~20240301184412.1845) > Target: x86_64-pc-linux-gnu > Thread model: posix > InstalledDir: /usr/lib/llvm-19/bin `$ lldb --version` > lldb version 19.0.0 `$ cat small.c` > typedef struct > { > int baddr; > } mstruct_t; > > static struct > { > unsigned int mapnum; > mstruct_t unused; > } mtab; > > static mstruct_t *mactab = &mtab.unused; > > int > main(void) > { > int i; > int addr; > > for (i=1; i <= mtab.mapnum; i++) > if (addr < mactab[i].baddr) > break; > return 0; > } `$ clang -O0 -g small.c; lldb a.out` > (lldb) target create "a.out" > Current executable set to '/root/a.out' (x86_64). > (lldb) b main > Breakpoint 1: where = a.out`main + 11 at small.c:20:9, address = 0x000000000000113b > (lldb) r > Process 26442 launched: '/root/a.out' (x86_64) > [1344/3230] Manually indexing DWARF: libc.so.6... The code you provided is causing LLDB to hang after setting a breakpoint at main and attempting to run the program.

[bulbazord]

I tried to reproduce this on macOS with top-of-tree LLDB and Clang. I wasn't able to hit the same issue, so it's possible the issue is specific to Linux (or even Ubuntu since you're using Ubuntu clang and Ubuntu lldb).

[xgupta]

Does not reproduce on arch linux with latest trunk of LLDB and Clang.

[jimingham]

This is happening during manual indexing. I'm surprised we're doing that anymore on up to date toolchains. Now that the index tables are part of standard DWARF, it is much better to use that...

Anyway, to reproduce this you're going to have to turn off emission of the DWARF index tables.