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xkbvalidate: Don't rely on GNU extensions

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The only reason why I was using _GNU_SOURCE was because of vasprintf(),
so getting rid of that extension should make the source way more
portable.

When using vsnprintf() with a null pointer for the output buffer and a
size of 0, I wasn't quite sure whether this would be undefined
behaviour, so I looked it up in the C11 standard.

In section 7.21.6.5, it explicitly mentions this case, so we're lucky:

  If n is zero, nothing is written, and s may be a null pointer.

Additionally, section 7.21.6.12 writes the following about vsnprintf():

  The vsnprintf function does not invoke the va_end macro.

So to be sure to avoid undefined behaviour I subsequently added the
corresponding va_end() calls.

With this, the platforms attribute is now "unix", because the program
should now even run on OS X, even though it usually wouldn't be needed.

Signed-off-by: aszlig <aszlig@nix.build>
This commit is contained in:
aszlig 2019-08-15 00:06:51 +02:00
parent 77e8a12755
commit 1964b0c1b1
No known key found for this signature in database
GPG Key ID: 684089CE67EBB691
2 changed files with 20 additions and 5 deletions
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4
pkgs/tools/X11/xkbvalidate/default.nix
View File

@ -5,11 +5,11 @@ runCommandCC "xkbvalidate" {
meta = {
description = "NixOS tool to validate X keyboard configuration";
license = lib.licenses.mit;
platforms = lib.platforms.linux;
platforms = lib.platforms.unix;
maintainers = [ lib.maintainers.aszlig ];
};
} ''
mkdir -p "$out/bin"
$CC -std=gnu11 -Wall -pedantic -lxkbcommon ${./xkbvalidate.c} \
$CC -std=c11 -Wall -pedantic -lxkbcommon ${./xkbvalidate.c} \
-o "$out/bin/validate"
''

21
pkgs/tools/X11/xkbvalidate/xkbvalidate.c
View File

@ -1,4 +1,3 @@
#define _GNU_SOURCE
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
@ -14,6 +13,9 @@ static bool log_alloc_success = true;
static void add_log(struct xkb_context *ctx, enum xkb_log_level level,
const char *fmt, va_list args)
{
size_t buflen;
va_list tmpargs;
log_buffer_size++;
if (log_buffer == NULL)
@ -28,11 +30,24 @@ static void add_log(struct xkb_context *ctx, enum xkb_log_level level,
return;
}
if (vasprintf(&log_buffer[log_buffer_size - 1], fmt, args) == -1) {
/* Unfortunately, vasprintf() is a GNU extension and thus not very
* portable, so let's first get the required buffer size using a dummy
* vsnprintf and afterwards allocate the returned amount of bytes.
*
* We also need to make a copy of the args, because the value of the args
* will be indeterminate after the return.
*/
va_copy(tmpargs, args);
buflen = vsnprintf(NULL, 0, fmt, tmpargs);
va_end(tmpargs);
log_buffer[log_buffer_size - 1] = malloc(++buflen);
if (vsnprintf(log_buffer[log_buffer_size - 1], buflen, fmt, args) == -1) {
perror("log line alloc");
log_alloc_success = false;
return;
}
va_end(args);
}
static void print_logs(void)