Disable debug builds.

Test function pointer compatibility.

appveyor.yml

diff --git a/appveyor.yml b/appveyor.yml
index 9954edf..d62fe49 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -7,10 +7,10 @@
       TRIPLET: x64-windows
       CMAKE_OPTS: "-DBUILD_SHARED_LIBS=off"
       CMAKE_CONFIG: Release
-    - GENERATOR: "Visual Studio 15 2017 Win64"
-      TRIPLET: x64-windows
-      CMAKE_OPTS: "-DBUILD_SHARED_LIBS=off"
-      CMAKE_CONFIG: Debug
+#    - GENERATOR: "Visual Studio 15 2017 Win64"
+#      TRIPLET: x64-windows
+#      CMAKE_OPTS: "-DBUILD_SHARED_LIBS=off"
+#      CMAKE_CONFIG: Debug
     - GENERATOR: "Visual Studio 15 2017 Win64"
       TRIPLET: x64-uwp
       CMAKE_OPTS: "-DCMAKE_SYSTEM_NAME=WindowsStore -DCMAKE_SYSTEM_VERSION=10.0"
@@ -19,10 +19,10 @@
       TRIPLET: x86-windows
       CMAKE_OPTS: "-DBUILD_SHARED_LIBS=off"
       CMAKE_CONFIG: Release
-    - GENERATOR: "Visual Studio 15 2017"
-      TRIPLET: x86-windows
-      CMAKE_OPTS: "-DBUILD_SHARED_LIBS=off"
-      CMAKE_CONFIG: Debug
+#    - GENERATOR: "Visual Studio 15 2017"
+#      TRIPLET: x86-windows
+#      CMAKE_OPTS: "-DBUILD_SHARED_LIBS=off"
+#      CMAKE_CONFIG: Debug
     - GENERATOR: "Visual Studio 15 2017"
       TRIPLET: x86-uwp
       CMAKE_OPTS: "-DCMAKE_SYSTEM_NAME=WindowsStore -DCMAKE_SYSTEM_VERSION=10.0"

lib/zip_source_file_win32_ansi.c

diff --git a/lib/zip_source_file_win32_ansi.c b/lib/zip_source_file_win32_ansi.c
index 1869a12..9e9b731 100644
--- a/lib/zip_source_file_win32_ansi.c
+++ b/lib/zip_source_file_win32_ansi.c
@@ -36,6 +36,27 @@
 static char *ansi_allocate_tempname(const char *name, size_t extra_chars, size_t *lengthp);
 static void ansi_make_tempname(char *buf, size_t len, const char *name, zip_uint32_t i);
 
+struct test {
+    DWORD (__stdcall *get_file_attributes)(const void *name);
+};
+
+struct test test_a = {
+    GetFileAttributesA
+};
+
+struct test test_w = {
+    GetFileAttributesW
+};
+
+static
+DWORD __stdcall *get_file_attributes_own(const void *name) {
+    return 0;
+}
+
+struct test test_own = {
+    get_file_attributes_own
+};
+
 zip_source_file_win32_write_operations_t ops_ansi = {
     ansi_allocate_tempname,
     CreateFileA,