libmicrohttpd2

commit 336517d01ce8414d81c71f00a0fa16b54bb26ca8
parent f0fecd1b5e816bbed5f45778dc1abd3148e4d698
Author: Evgeny Grin (Karlson2k) <k2k@drgrin.dev>
Date:   Thu, 29 Oct 2026 22:04:38 +0100

Replaced variable-length array parameters with pointers

Some function parameters were declared as variable-length arrays even
though the corresponding size can be zero. A VLA bound must be greater
than zero, so valid zero-size calls triggered undefined behaviour before
the function body was entered.

Replaced the array declarations with plain pointers and retained their
size annotations using MHD_FN_PAR_IN_SIZE_(). This also permits NULL
pointers when the corresponding size is zero.

Patch provided by Sami Jawhar on the mailing list.

Diffstat:
M
doc/manual/responses.inc
 | 
4
++--
M
src/include/microhttpd2.h
 | 
10
++++++----
M
src/include/microhttpd2_main.h.in
 | 
7
++++---
M
src/include/microhttpd2_preamble.h.in
 | 
3
++-
M
src/mhd2/response_from.c
 | 
11
++++++-----

5 files changed, 20 insertions(+), 15 deletions(-)
diff --git a/doc/manual/responses.inc b/doc/manual/responses.inc
@@ -218,7 +218,7 @@ Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 @anchor{MHD_response_from_buffer_copy}
-@deftypefun {struct MHD_Response *} MHD_response_from_buffer_copy (enum MHD_HTTP_StatusCode sc, size_t buffer_size, const char buffer[buffer_size])
+@deftypefun {struct MHD_Response *} MHD_response_from_buffer_copy (enum MHD_HTTP_StatusCode sc, size_t buffer_size, const char *buffer)
 
 Create a response object from an ephemeral @var{buffer}. The data
 in the @var{buffer} will be copied into internal storage of MHD.
@@ -268,7 +268,7 @@ use to implement this.}
 @cindex scatter write
 @cindex writev
 @anchor{MHD_response_from_iovec}
-@deftypefun {struct MHD_Response *} MHD_response_from_iovec (enum MHD_HTTP_StatusCode sc, unsigned int iov_count, const struct MHD_IoVec iov[iov_count], MHD_FreeCallback free_cb, void *free_cb_cls)
+@deftypefun {struct MHD_Response *} MHD_response_from_iovec (enum MHD_HTTP_StatusCode sc, unsigned int iov_count, const struct MHD_IoVec *iov, MHD_FreeCallback free_cb, void *free_cb_cls)
 
 Create a response object from an array of memory buffers.
 @table @var
diff --git a/src/include/microhttpd2.h b/src/include/microhttpd2.h
@@ -3912,7 +3912,8 @@ MHD_EXTERN_ enum MHD_StatusCode
 MHD_connection_set_psk (
   struct MHD_ServerCredentialsContext *mscc,
   size_t psk_size,
-  const /*void? */ char psk[MHD_FN_PAR_DYN_ARR_SIZE_ (psk_size)]);
+  const /*void? */ char *psk)
+MHD_FN_PAR_IN_SIZE_ (3, 2);
 
 #define MHD_connection_set_psk_unavailable(mscc) \
         MHD_connection_set_psk (mscc, 0, NULL)
@@ -6648,7 +6649,7 @@ MHD_EXTERN_ struct MHD_Response *
 MHD_response_from_buffer_copy (
   enum MHD_HTTP_StatusCode sc,
   size_t buffer_size,
-  const char buffer[MHD_FN_PAR_DYN_ARR_SIZE_ (buffer_size)])
+  const char *buffer)
 MHD_FN_PAR_IN_SIZE_ (3, 2);
 
 
@@ -6696,9 +6697,10 @@ MHD_EXTERN_ struct MHD_Response *
 MHD_response_from_iovec (
   enum MHD_HTTP_StatusCode sc,
   unsigned int iov_count,
-  const struct MHD_IoVec iov[MHD_FN_PAR_DYN_ARR_SIZE_ (iov_count)],
+  const struct MHD_IoVec *iov,
   MHD_FreeCallback free_cb,
-  void *free_cb_cls);
+  void *free_cb_cls)
+MHD_FN_PAR_IN_SIZE_ (3, 2);
 
 
 /**
diff --git a/src/include/microhttpd2_main.h.in b/src/include/microhttpd2_main.h.in
@@ -1589,7 +1589,7 @@ MHD_EXTERN_ struct MHD_Response *
 MHD_response_from_buffer_copy (
   enum MHD_HTTP_StatusCode sc,
   size_t buffer_size,
-  const char buffer[MHD_FN_PAR_DYN_ARR_SIZE_ (buffer_size)])
+  const char *buffer)
 MHD_FN_PAR_IN_SIZE_ (3, 2);
 
 
@@ -1637,9 +1637,10 @@ MHD_EXTERN_ struct MHD_Response *
 MHD_response_from_iovec (
   enum MHD_HTTP_StatusCode sc,
   unsigned int iov_count,
-  const struct MHD_IoVec iov[MHD_FN_PAR_DYN_ARR_SIZE_ (iov_count)],
+  const struct MHD_IoVec *iov,
   MHD_FreeCallback free_cb,
-  void *free_cb_cls);
+  void *free_cb_cls)
+MHD_FN_PAR_IN_SIZE_ (3, 2);
 
 
 /**
diff --git a/src/include/microhttpd2_preamble.h.in b/src/include/microhttpd2_preamble.h.in
@@ -3912,7 +3912,8 @@ MHD_EXTERN_ enum MHD_StatusCode
 MHD_connection_set_psk (
   struct MHD_ServerCredentialsContext *mscc,
   size_t psk_size,
-  const /*void? */ char psk[MHD_FN_PAR_DYN_ARR_SIZE_ (psk_size)]);
+  const /*void? */ char *psk)
+MHD_FN_PAR_IN_SIZE_ (3, 2);
 
 #define MHD_connection_set_psk_unavailable(mscc) \
         MHD_connection_set_psk (mscc, 0, NULL)
diff --git a/src/mhd2/response_from.c b/src/mhd2/response_from.c
@@ -200,7 +200,7 @@ MHD_FN_PAR_IN_SIZE_ (3, 2) struct MHD_Response *
 MHD_response_from_buffer_copy (
   enum MHD_HTTP_StatusCode sc,
   size_t buffer_size,
-  const char buffer[MHD_FN_PAR_DYN_ARR_SIZE_ (buffer_size)])
+  const char *buffer)
 {
   struct MHD_Response *restrict res;
   const unsigned char *buf_copy;
@@ -242,11 +242,11 @@ MHD_response_from_buffer_copy (
 }
 
 
-static struct MHD_Response *
+static MHD_FN_PAR_IN_SIZE_ (3, 2) struct MHD_Response *
 response_from_iovec_inner (
   enum MHD_HTTP_StatusCode sc,
   unsigned int iov_count,
-  const struct MHD_IoVec iov[MHD_FN_PAR_DYN_ARR_SIZE_ (iov_count)],
+  const struct MHD_IoVec *iov,
   MHD_FreeCallback free_cb,
   void *free_cb_cls)
 {
@@ -352,11 +352,12 @@ response_from_iovec_inner (
 }
 
 
-MHD_EXTERN_ struct MHD_Response *
+MHD_EXTERN_
+MHD_FN_PAR_IN_SIZE_ (3, 2) struct MHD_Response *
 MHD_response_from_iovec (
   enum MHD_HTTP_StatusCode sc,
   unsigned int iov_count,
-  const struct MHD_IoVec iov[MHD_FN_PAR_DYN_ARR_SIZE_ (iov_count)],
+  const struct MHD_IoVec *iov,
   MHD_FreeCallback free_cb,
   void *free_cb_cls)
 {