Cannot continue over exec

[multun]

When running a shell script which execs a binary, nothing gets printed on stdout with rr replay.

Environment

Tested on an Haswell laptop, on master and the last release

Reproducer

cat >hello-world.c <<EOF
#include <stdio.h>

int main() {
  puts("hello world");
  return 0;
}
EOF
make hello-world

cat >wrapper.sh <<EOF
#!/bin/sh
exec "./hello-world"
EOF
chmod +x wrapper.sh

rr record ./hello-world
rr replay
# hello world gets printed to stdout
rr record ./wrapper.sh
rr replay
[SNIP]
(rr) continue
# nothing

[dzaima]

The problem is that rr is unable to continue over exec... syscalls; a workaround I've used before is to run when-ticks, and do seek-ticks (result of when-ticks plus one), but it's still funky. Haven't looked into why.

Related issue (which doesn't happen as-is anymore due to it now freezing on the exec, but using the seek-ticks thing it still results in 'g' packet errors): https://github.com/rr-debugger/rr/issues/2961

[multun]

The linked issue says something about 32 / 64 bits transitions, and this example doesn't involve anything like it. Didn't it work at some point?

[dzaima]

Wouldn't be surprised if it worked before, as it seems that in that issue it indeed continued over the exec transition, but it doesn't anymore.

[rocallahan]

I think continuing through exec has never worked with rr.

It might be possible to fix this. gdb can do it. I don't know what we'd have to do in rr.