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new d5563b10ccd include/limits.h: Set IOV_MAX to 1024
d5563b10ccd is described below
commit d5563b10ccd6dcccd68bc97d0cc663d5b5c278ee
Author: Marco Casaroli <[email protected]>
AuthorDate: Mon Nov 2 12:41:54 2026 +0100
include/limits.h: Set IOV_MAX to 1024
IOV_MAX is INT_MAX because NuttX has no upper limit on the number of I/O
vectors of readv() and writev(). But programs declare arrays of IOV_MAX
vectors, also on the stack. With INT_MAX such an array has 32 GiB on a
64-bit target, and the program stops with a segmentation fault when it
clears the array. On a 32-bit target the array does not compile.
IOV_MAX is now 1024, the value of Linux and the BSDs. POSIX requires at
least 16 (_XOPEN_IOV_MAX). sysconf(_SC_IOV_MAX) now gives it (before: -1
with ENOSYS). readv() and writev() still accept more vectors.
Assisted-by: Claude Code:claude-opus-5-5
Signed-off-by: Marco Casaroli <[email protected]>
---
include/limits.h | 8 ++++----
libs/libc/unistd/lib_sysconf.c | 3 +++
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/limits.h b/include/limits.h
index 44140a1e3e8..8ae80cec664 100644
--- a/include/limits.h
+++ b/include/limits.h
@@ -279,11 +279,11 @@
#define PTHREAD_DESTRUCTOR_ITERATIONS _POSIX_THREAD_DESTRUCTOR_ITERATIONS
-/* Required for readv() and writev() */
-
-/* There really is no upper limit on the number of vectors */
+/* Required for readv() and writev(). NuttX has no upper limit, but programs
+ * declare arrays of IOV_MAX vectors: use the value of Linux and the BSDs.
+ */
-#define IOV_MAX INT_MAX
+#define IOV_MAX 1024
#define HOST_NAME_MAX CONFIG_HOST_NAME_MAX
diff --git a/libs/libc/unistd/lib_sysconf.c b/libs/libc/unistd/lib_sysconf.c
index 1e3460b1bae..b577d053768 100644
--- a/libs/libc/unistd/lib_sysconf.c
+++ b/libs/libc/unistd/lib_sysconf.c
@@ -289,6 +289,9 @@ long sysconf(int name)
case _SC_AIO_LISTIO_MAX:
return AIO_LISTIO_MAX;
+ case _SC_IOV_MAX:
+ return IOV_MAX;
+
default:
#if 0 /* Assume valid but not implemented for the time being */
errcode = EINVAL;
