[pve-devel] [PATCH qemu] Add format attributes to function candidates

[pve-devel] [PATCH qemu] Add format attributes to function candidates

[Filip Schauer]

Add format attributes to functions that take printf-like arguments. This
provides additional compile-time checking that the correct parameters
are passed to the functions.

This fixes compiler warnings generated by the -Wsuggest-attribute=format
flag.

Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
 ...-async-for-background-state-snapshots.patch | 13 ++++++++++++-
 ...PVE-Backup-add-vma-backup-format-code.patch | 18 ++++++++++++++----
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch b/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
index 7be1af4..68c5627 100644
--- a/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
+++ b/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
@@ -142,7 +142,7 @@ new file mode 100644
 index 0000000000..ac1fac6378
 --- /dev/null
 +++ b/migration/savevm-async.c
-@@ -0,0 +1,533 @@
+@@ -0,0 +1,544 @@
 +#include "qemu/osdep.h"
 +#include "migration/channel-savevm-async.h"
 +#include "migration/migration.h"
@@ -177,6 +177,16 @@ index 0000000000..ac1fac6378
 +    do { } while (0)
 +#endif
 +
++#ifdef __GNUC__
++#if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
++#define PRINTF(i, j)    __attribute__((format (gnu_printf, i, j)))
++#else
++#define PRINTF(i, j)    __attribute__((format (printf, i, j)))
++#endif
++#else
++#define PRINTF(i, j)
++#endif
++
 +enum {
 +    SAVE_STATE_DONE,
 +    SAVE_STATE_ERROR,
@@ -275,6 +285,7 @@ index 0000000000..ac1fac6378
 +    return ret;
 +}
 +
++static void save_snapshot_error(const char *fmt, ...) PRINTF(1, 2);
 +static void save_snapshot_error(const char *fmt, ...)
 +{
 +    va_list ap;
diff --git a/debian/patches/pve/0027-PVE-Backup-add-vma-backup-format-code.patch b/debian/patches/pve/0027-PVE-Backup-add-vma-backup-format-code.patch
index 8471a6f..5dcd866 100644
--- a/debian/patches/pve/0027-PVE-Backup-add-vma-backup-format-code.patch
+++ b/debian/patches/pve/0027-PVE-Backup-add-vma-backup-format-code.patch
@@ -2314,13 +2314,13 @@ index 0000000000..304f02bc84
 +        ret = blk_co_preadv(job->target, start * VMA_CLUSTER_SIZE,
 +                            readlen, &qiov, 0);
 +        if (ret < 0) {
-+            vma_writer_set_error(job->vmaw, "read error", -1);
++            vma_writer_set_error(job->vmaw, "read error");
 +            goto out;
 +        }
 +
 +        size_t zb = 0;
 +        if (vma_writer_write(job->vmaw, job->dev_id, start, buf, &zb) < 0) {
-+            vma_writer_set_error(job->vmaw, "backup_dump_cb vma_writer_write failed", -1);
++            vma_writer_set_error(job->vmaw, "backup_dump_cb vma_writer_write failed");
 +            goto out;
 +        }
 +    }
@@ -2622,7 +2622,7 @@ new file mode 100644
 index 0000000000..1b62859165
 --- /dev/null
 +++ b/vma.h
-@@ -0,0 +1,150 @@
+@@ -0,0 +1,160 @@
 +/*
 + * VMA: Virtual Machine Archive
 + *
@@ -2643,6 +2643,16 @@ index 0000000000..1b62859165
 +#include "qapi/error.h"
 +#include "block/block.h"
 +
++#ifdef __GNUC__
++#if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
++#define PRINTF(i, j)    __attribute__((format (gnu_printf, i, j)))
++#else
++#define PRINTF(i, j)    __attribute__((format (printf, i, j)))
++#endif
++#else
++#define PRINTF(i, j)
++#endif
++
 +#define VMA_BLOCK_BITS 12
 +#define VMA_BLOCK_SIZE (1<<VMA_BLOCK_BITS)
 +#define VMA_CLUSTER_BITS (VMA_BLOCK_BITS+4)
@@ -2757,7 +2767,7 @@ index 0000000000..1b62859165
 +int coroutine_fn vma_writer_flush_output(VmaWriter *vmaw);
 +
 +int vma_writer_get_status(VmaWriter *vmaw, VmaStatus *status);
-+void vma_writer_set_error(VmaWriter *vmaw, const char *fmt, ...);
++void vma_writer_set_error(VmaWriter *vmaw, const char *fmt, ...) PRINTF(2, 3);
 +
 +
 +VmaReader *vma_reader_create(const char *filename, Error **errp);
-- 
2.39.2

Re: [pve-devel] [PATCH qemu] Add format attributes to function candidates

[Fiona Ebner]

Am 07.08.23 um 11:18 schrieb Filip Schauer:
> Add format attributes to functions that take printf-like arguments. This
> provides additional compile-time checking that the correct parameters
> are passed to the functions.
> 
> This fixes compiler warnings generated by the -Wsuggest-attribute=format
> flag.
>

Which will actually be treated as an error after rebasing to QEMU 8.1,
so I already have a change for this lined-up. If you want, you can send
a v2 with my suggestion below, otherwise I'll just do the change when
rebasing to 8.1.

> @@ -177,6 +177,16 @@ index 0000000000..ac1fac6378
>  +    do { } while (0)
>  +#endif
>  +
> ++#ifdef __GNUC__
> ++#if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
> ++#define PRINTF(i, j)    __attribute__((format (gnu_printf, i, j)))
> ++#else
> ++#define PRINTF(i, j)    __attribute__((format (printf, i, j)))
> ++#endif
> ++#else
> ++#define PRINTF(i, j)
> ++#endif
> ++

Note that QEMU already defines and uses a macro G_GNUC_PRINTF for this,
so I'd really like to use that in our patches too, no need to cook up
our own :)