From 963b0eeea6ec10b7cceacdde920610f5455158c0 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 11 Dec 2015 01:07:56 +0530
Subject: [PATCH] Nicer error message when loading the Universal CRT fails

---
 setup/installer/windows/main.c | 38 +++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/setup/installer/windows/main.c b/setup/installer/windows/main.c
index 4cb2818fb3..18a64b33dc 100644
--- a/setup/installer/windows/main.c
+++ b/setup/installer/windows/main.c
@@ -58,38 +58,52 @@ static ENTRYPROC load_launcher_dll() {
     int i = 0;
     DWORD sz = 0; 
     HMODULE dll = 0;
-    ENTRYPROC entrypoint = 0;
+    ENTRYPROC entrypoint = NULL;
 
-    if ((sz = GetModuleFileNameW(NULL, buf, MAX_PATH)) >= MAX_PATH - 30)
-        ExitProcess(show_error(L"Installation directory path too long", L"", 1));
+    if ((sz = GetModuleFileNameW(NULL, buf, MAX_PATH)) >= MAX_PATH - 30) {
+        show_error(L"Installation directory path too long", L"", 1);
+        return NULL;
+    }
 
     while (sz > 0) {
         if (buf[sz] == L'\\' || buf[sz] == L'/') break;
         sz--;
     }
-    if (sz <= 0)
-        ExitProcess(show_error(L"Executable path has no path separators", L"", 1));
+    if (sz <= 0) {
+        show_error(L"Executable path has no path separators", L"", 1);
+        return NULL;
+    }
     buf[sz+1] = L'a'; buf[sz+2] = L'p'; buf[sz+3] = L'p'; buf[sz+4] = L'\\';
     buf[sz+5] = L'D'; buf[sz+6] = L'L'; buf[sz+7] = L'L'; buf[sz+8] = L's';
     buf[sz+9] = 0; buf[sz+10] = 0;
     if (SetDllDirectoryW(buf) == 0) {
         show_last_error(L"Failed to set DLL directory");
-        ExitProcess(1);
+        return NULL;
+    }
+    if (!LoadLibraryW(L"ucrtbase.dll")) {
+        show_last_error(L"Unable to find ucrtbase.dll. You should install all Windows updates on your computer to get this file.");
+        return NULL;
+    }
+    if (!(dll = LoadLibraryW(L"calibre-launcher.dll"))) {
+        show_last_error(L"Failed to load: calibre-launcher.dll");
+        return NULL;
+    }
+    if (!(entrypoint = (ENTRYPROC) GetProcAddress(dll, "execute_python_entrypoint"))) {
+        show_last_error(L"Failed to get the calibre-launcher dll entry point");
+        return NULL;
     }
-    dll = LoadLibraryW(L"calibre-launcher.dll");
-    if (!dll) ExitProcess(show_last_error(L"Failed to get the calibre-launcher dll handle"));
-    entrypoint = (ENTRYPROC) GetProcAddress(dll, "execute_python_entrypoint");
-    if (!entrypoint) ExitProcess(show_last_error(L"Failed to get the calibre-launcher dll entry point"));
     return entrypoint;
 }
 
 int __stdcall start_here() {
     int ret = 0;
+    ENTRYPROC entrypoint = load_launcher_dll();
+    if (!entrypoint) return 1;
 #ifdef GUI_APP
     // This should really be returning the value set in the WM_QUIT message, but I cannot be bothered figuring out how to get that.
-    load_launcher_dll()(BASENAME, MODULE, FUNCTION, 1);
+    entrypoint(BASENAME, MODULE, FUNCTION, 1);
 #else
-    ret = load_launcher_dll()(BASENAME, MODULE, FUNCTION, 0);
+    ret = entrypoint(BASENAME, MODULE, FUNCTION, 0);
 #endif
     ExitProcess(ret);
     return ret;