Calling error_report() from within a function using Error to return
error information is almost always wrong. Example:
QMP command qmp_migrate()
calls rdma_start_outgoing_migration()
calls qemu_rdma_source_init()
calls qemu_rdma_reg_control()
The first four have an Error **errp parameter, and use it to return
error information. Good.
The last one does not. Instead, qemu_rdma_reg_control() calls
error_report() on failure:
error_report("qemu_rdma_reg_control failed");
return -1;
Its caller qemu_rdma_source_init() detects the failure and sets an
error:
ret = qemu_rdma_reg_control(rdma, idx);
if (ret) {
error_setg(temp, "RDMA ERROR: rdma migration: error registering %d
control!",
idx);
goto err_rdma_source_init;
}
Because of this, QMP command migrate spams stderr on this particular
failure. Inappropriate.
Easy enough to fix, but I'm after the error pattern, not a single
instance that happened to catch my eye.
Problem: find call chains from functions using Error to error_report().
Two sub-problems:
1. Find functions using Error
Doesn't have to be perfect. I have a simple Coccinelle script
(appended) that spits out some 4400 functions. I run it like
$ spatch --sp-file find-error-fns.cocci --macro-file
scripts/cocci-macro-file.h `git-grep -Fl 'Error **' \*.[ch]`
2. Find call chains from these functions to error_report()
I'm hoping vrc can do that for me. How?
Here's my find-error-fns.cocci:
@r@
identifier fn, errp;
position p;
@@
fn@p(..., Error **errp, ...)
{
...
}
@script:python@
fn << r.fn;
p << r.p;
@@
print(f'{p[0].file}:{p[0].line}:{p[0].column}:{fn}')
