While reviewing the previous whitespace-only patch, I noticed several casts that are semantically unnecessary in C: - converting pointers to and from void* does not need a cast except for function pointers or when also casting away const (different from C++ where casts to or from void* are required for type safety); includes cases like python PyCapsule code which uses void* - casting away const on a string literal (in C, string literals are typed 'char *', different from C++ where they are 'const char *'; that said, C says it is still undefined behavior to modify their contents, so string literals should generally be only assigned to 'const char *' variables or passed to functions that promise not to modify contents); includes cases like ocaml's struct custom_operations using 'const char *' as its member type (where casting away const just to re-add it is pointless) - casts used to document what would otherwise be implicit type conversions when assigning to integers of a different type or passing function parameters not through varargs. While this can be useful for documentation purposes, it can also mask bugs when the cast uses the wrong intermediate type only to be implicitly converted back to the destination type, and it is often easier to use optional compiler warning flags to catch instances of unintended truncation or sign extension by implicit conversions. Minimizing semantically unneeded casts lets the remaining casts stand out for why they are necessary: casting aways const, casts between pointer aliases (such as struct sockaddr*, char* vs unsigned char*, ...), and scalars passed through vargs in printf-like functions. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- generator/Python.ml | 2 +- generator/states-connect-socket-activation.c | 2 +- generator/states-issue-command.c | 2 +- lib/utils.c | 4 ++-- python/handle.c | 2 +- ocaml/nbd-c.h | 6 +++--- tests/opt-set-meta.c | 2 +- copy/main.c | 6 +++--- fuse/nbdfuse.c | 4 ++-- fuse/operations.c | 2 +- ublk/nbdublk.c | 4 ++-- 11 files changed, 18 insertions(+), 18 deletions(-) diff --git a/generator/Python.ml b/generator/Python.ml index b73f9782..c81878de 100644 --- a/generator/Python.ml +++ b/generator/Python.ml @@ -49,7 +49,7 @@ let { assert (obj); assert (obj != Py_None); - return (struct nbd_handle *)PyCapsule_GetPointer(obj, \"nbd_handle\"); + return PyCapsule_GetPointer(obj, \"nbd_handle\"); } /* nbd.Error exception. */ diff --git a/generator/states-connect-socket-activation.c b/generator/states-connect-socket-activation.c index 98a39c0e..40a3528c 100644 --- a/generator/states-connect-socket-activation.c +++ b/generator/states-connect-socket-activation.c @@ -294,7 +294,7 @@ CONNECT_SA.START: char buf[32]; const char *v = - nbd_internal_fork_safe_itoa ((long)getpid (), buf, sizeof buf); + nbd_internal_fork_safe_itoa (getpid (), buf, sizeof buf); NBD_INTERNAL_FORK_SAFE_ASSERT (strlen (v) <= sact_var[pid_ofs].value_len); strcpy (env.ptr[pid_ofs] + sact_var[pid_ofs].prefix_len, v); diff --git a/generator/states-issue-command.c b/generator/states-issue-command.c index 34ef4652..111e131c 100644 --- a/generator/states-issue-command.c +++ b/generator/states-issue-command.c @@ -46,7 +46,7 @@ ISSUE_COMMAND.START: h->request.type = htobe16 (cmd->type); h->request.handle = htobe64 (cmd->cookie); h->request.offset = htobe64 (cmd->offset); - h->request.count = htobe32 ((uint32_t)cmd->count); + h->request.count = htobe32 (cmd->count); h->chunks_sent++; h->wbuf = &h->request; h->wlen = sizeof (h->request); diff --git a/lib/utils.c b/lib/utils.c index e3e13cdd..5df5ae51 100644 --- a/lib/utils.c +++ b/lib/utils.c @@ -154,7 +154,7 @@ nbd_internal_set_querylist (struct nbd_handle *h, char **queries) const char * nbd_internal_fork_safe_itoa (long v, char *buf, size_t bufsize) { - unsigned long uv = (unsigned long)v; + unsigned long uv = v; size_t i = bufsize - 1; bool neg = false; @@ -282,7 +282,7 @@ nbd_internal_fork_safe_perror (const char *s) #endif #endif if (!m) - m = nbd_internal_fork_safe_itoa ((long)errno, buf, sizeof buf); + m = nbd_internal_fork_safe_itoa (errno, buf, sizeof buf); xwritel (STDERR_FILENO, s, ": ", m, "\n", (char *)NULL); /* Restore original errno in case it was disturbed by the system diff --git a/python/handle.c b/python/handle.c index 8ff6ba81..548f2dfe 100644 --- a/python/handle.c +++ b/python/handle.c @@ -46,7 +46,7 @@ static inline PyObject * put_handle (struct nbd_handle *h) { assert (h); - return PyCapsule_New ((void *)h, "nbd_handle", NULL); + return PyCapsule_New (h, "nbd_handle", NULL); } PyObject * diff --git a/ocaml/nbd-c.h b/ocaml/nbd-c.h index 0cbe36d1..e3abb912 100644 --- a/ocaml/nbd-c.h +++ b/ocaml/nbd-c.h @@ -49,7 +49,7 @@ static inline value caml_alloc_initialized_string (mlsize_t len, const char *p) { value sv = caml_alloc_string (len); - memcpy ((char *)String_val (sv), p, len); + memcpy (String_val (sv), p, len); return sv; } #endif @@ -70,7 +70,7 @@ extern void nbd_internal_ocaml_exception_in_wrapper (const char *, value); #define NBD_val(v) (*((struct nbd_handle **)Data_custom_val (v))) static struct custom_operations libnbd_custom_operations = { - (char *)"libnbd_custom_operations", + "libnbd_custom_operations", nbd_internal_ocaml_handle_finalize, custom_compare_default, custom_hash_default, @@ -110,7 +110,7 @@ struct nbd_buffer { #define NBD_buffer_val(v) ((struct nbd_buffer *)Data_custom_val (v)) static struct custom_operations nbd_buffer_custom_operations = { - (char *)"nbd_buffer_custom_operations", + "nbd_buffer_custom_operations", nbd_internal_ocaml_buffer_finalize, custom_compare_default, custom_hash_default, diff --git a/tests/opt-set-meta.c b/tests/opt-set-meta.c index 1bd60a9c..06f503af 100644 --- a/tests/opt-set-meta.c +++ b/tests/opt-set-meta.c @@ -219,7 +219,7 @@ main (int argc, char *argv[]) * or newer with its --no-sr kill switch. */ requires ("nbdkit --no-sr --help"); - args[ARRAY_SIZE (args) - 2] = (char *)"--no-sr"; + args[ARRAY_SIZE (args) - 2] = "--no-sr"; nbd = nbd_create (); if (nbd == NULL || nbd_set_opt_mode (nbd, true) == -1 || diff --git a/copy/main.c b/copy/main.c index 391c0c4f..9449440e 100644 --- a/copy/main.c +++ b/copy/main.c @@ -371,7 +371,7 @@ main (int argc, char *argv[]) #else t = 1; #endif - threads = (unsigned)t; + threads = t; } if (synchronous) @@ -534,7 +534,7 @@ open_local (const char *filename, direction d) } if (S_ISREG (stat.st_mode)) /* Regular file. */ return file_create (filename, fd, - stat.st_size, (uint64_t)stat.st_blksize, false, d); + stat.st_size, stat.st_blksize, false, d); else if (S_ISBLK (stat.st_mode)) { /* Block device. */ unsigned int blkioopt; @@ -549,7 +549,7 @@ open_local (const char *filename, direction d) #endif return file_create (filename, fd, - stat.st_size, (uint64_t)blkioopt, true, d); + stat.st_size, blkioopt, true, d); } else { /* Probably stdin/stdout, a pipe or a socket. */ synchronous = true; /* Force synchronous mode for pipes. */ diff --git a/fuse/nbdfuse.c b/fuse/nbdfuse.c index 491f6db8..35d5ffac 100644 --- a/fuse/nbdfuse.c +++ b/fuse/nbdfuse.c @@ -415,7 +415,7 @@ main (int argc, char *argv[]) handles_append (&nbd, h); /* reserved above, so can't fail */ } } - connections = (unsigned)nbd.len; + connections = nbd.len; if (verbose) fprintf (stderr, "nbdfuse: connections=%u\n", connections); @@ -424,7 +424,7 @@ main (int argc, char *argv[]) fprintf (stderr, "%s\n", nbd_get_error ()); exit (EXIT_FAILURE); } - size = (uint64_t)ssize; + size = ssize; /* If the remote NBD server is readonly, then act as if the '-r' * flag was given on the nbdfuse command line. diff --git a/fuse/operations.c b/fuse/operations.c index 2d0634dc..e487d150 100644 --- a/fuse/operations.c +++ b/fuse/operations.c @@ -396,7 +396,7 @@ nbdfuse_read (const char *path, char *buf, CHECK_NBD_ASYNC_ERROR (nbd_aio_pread (h, buf, count, offset, cb, 0)); - return (int)count; + return count; } static int diff --git a/ublk/nbdublk.c b/ublk/nbdublk.c index b85ac609..2f097f3e 100644 --- a/ublk/nbdublk.c +++ b/ublk/nbdublk.c @@ -347,7 +347,7 @@ main (int argc, char *argv[]) handles_append (&nbd, h); /* reserved above, so can't fail */ } } - connections = (unsigned)nbd.len; + connections = nbd.len; /* Get the size and preferred block sizes. */ rs = nbd_get_size (nbd.ptr[0]); @@ -355,7 +355,7 @@ main (int argc, char *argv[]) fprintf (stderr, "%s\n", nbd_get_error ()); exit (EXIT_FAILURE); } - size = (uint64_t)rs; + size = rs; rs = nbd_get_block_size (nbd.ptr[0], LIBNBD_SIZE_MAXIMUM); if (rs <= 0 || rs > 64 * 1024 * 1024)

On Wed, May 24, 2023 at 10:00:03AM -0500, Eric Blake wrote: > diff --git a/copy/main.c b/copy/main.c > index 391c0c4f..9449440e 100644 > --- a/copy/main.c > +++ b/copy/main.c > @@ -371,7 +371,7 @@ main (int argc, char *argv[]) > #else > t = 1; > #endif > - threads = (unsigned)t; > + threads = t; This one doesn't give any warning about truncating from long (64 bits) to unsigned (32 bits)?

> diff --git a/fuse/nbdfuse.c b/fuse/nbdfuse.c > index 491f6db8..35d5ffac 100644 > --- a/fuse/nbdfuse.c > +++ b/fuse/nbdfuse.c > @@ -415,7 +415,7 @@ main (int argc, char *argv[]) > handles_append (&nbd, h); /* reserved above, so can't fail */ > } > } > - connections = (unsigned)nbd.len; > + connections = nbd.len; Similarly this would be size_t -> unsigned, also a truncation on 64 bit.

But if there are no warnings, then: Reviewed-by: Richard W.M. Jones <rjones(a)redhat.com&gt;