From f4ff41080719099eec3475d93aed4c1b70a5447a Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Thu, 19 Oct 2023 14:55:37 +0200
Subject: [PATCH] configure: check for the fseeko declaration too

... and make the code require both symbol and declaration.

This is because for Android, the symbol is always present in the lib at
build-time even when not actually available in run-time.

Assisted-by: Viktor Szakats
Reported-by: 12932 on github
Fixes #12086
Closes #12158
---
 CMakeLists.txt          |  4 ++++
 configure.ac            | 10 +++++++++-
 lib/curl_config.h.cmake |  3 +++
 lib/formdata.c          |  2 +-
 4 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9267543a24..04cffd78f3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1208,6 +1208,10 @@ check_symbol_exists(setlocale      "${CURL_INCLUDES}" HAVE_SETLOCALE)
 check_symbol_exists(setmode        "${CURL_INCLUDES}" HAVE_SETMODE)
 check_symbol_exists(setrlimit      "${CURL_INCLUDES}" HAVE_SETRLIMIT)
 
+if(HAVE_FSEEKO)
+  set(HAVE_DECL_FSEEKO 1)
+endif()
+
 if(NOT MSVC OR (MSVC_VERSION GREATER_EQUAL 1900))
   # earlier MSVC compilers had faulty snprintf implementations
   check_symbol_exists(snprintf       "stdio.h" HAVE_SNPRINTF)
diff --git a/configure.ac b/configure.ac
index 1861e1e59f..97b4d3e018 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3581,7 +3581,6 @@ AC_CHECK_DECLS([getpwuid_r], [], [AC_DEFINE(HAVE_DECL_GETPWUID_R_MISSING, 1, "Se
         [[#include <pwd.h>
           #include <sys/types.h>]])
 
-
 AC_CHECK_FUNCS([\
   _fseeki64 \
   arc4random \
@@ -3628,6 +3627,15 @@ AC_CHECK_FUNCS([\
   fi
 ])
 
+dnl On Android, the only way to know if fseeko can be used is to see if it is
+dnl declared or not (for this API level), as the symbol always exists in the
+dnl lib.
+AC_CHECK_DECL([fseeko],
+              [AC_DEFINE([HAVE_DECL_FSEEKO], [1],
+               [Define to 1 if you have the fseeko declaration])],
+              [],
+              [[#include <stdio.h>]])
+
 CURL_CHECK_NONBLOCKING_SOCKET
 
 dnl ************************************************************
diff --git a/lib/curl_config.h.cmake b/lib/curl_config.h.cmake
index 6df67d081b..e12e7a1242 100644
--- a/lib/curl_config.h.cmake
+++ b/lib/curl_config.h.cmake
@@ -211,6 +211,9 @@
 /* Define to 1 if you have the fseeko function. */
 #cmakedefine HAVE_FSEEKO 1
 
+/* Define to 1 if you have the fseeko declaration. */
+#cmakedefine HAVE_DECL_FSEEKO 1
+
 /* Define to 1 if you have the _fseeki64 function. */
 #cmakedefine HAVE__FSEEKI64 1
 
diff --git a/lib/formdata.c b/lib/formdata.c
index e40c4bcb03..9781029555 100644
--- a/lib/formdata.c
+++ b/lib/formdata.c
@@ -792,7 +792,7 @@ static CURLcode setname(curl_mimepart *part, const char *name, size_t len)
 /* wrap call to fseeko so it matches the calling convention of callback */
 static int fseeko_wrapper(void *stream, curl_off_t offset, int whence)
 {
-#if defined(HAVE_FSEEKO)
+#if defined(HAVE_FSEEKO) && defined(HAVE_DECL_FSEEKO)
   return fseeko(stream, (off_t)offset, whence);
 #elif defined(HAVE__FSEEKI64)
   return _fseeki64(stream, (__int64)offset, whence);