From fdf578d936abacafe2bfb8d08255a5093b1f1ea3 Mon Sep 17 00:00:00 2001
From: MatthiasWM <visualc.git@matthiasm.com>
Date: Fri, 15 Dec 2023 12:56:06 +0100
Subject: [PATCH] #840: Fixes fixed buffer size in Fl::args_to_utf8()
 (fl_call_main)

---
 src/fl_call_main.c | 38 ++++++++++++++++++++++++++++----------
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/src/fl_call_main.c b/src/fl_call_main.c
index de05b98d4..88049eec7 100644
--- a/src/fl_call_main.c
+++ b/src/fl_call_main.c
@@ -70,7 +70,6 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
   int i;
   int argc = 0;
   char** argv = NULL;
-  char strbuf[2048];
 
  /*
   * If we are compiling in debug mode, open a console window so
@@ -97,15 +96,34 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
 
   /* Convert the command line arguments to UTF-8 */
   for (i = 0; i < argc; i++) {
-    int ret = WideCharToMultiByte(CP_UTF8,        /* CodePage          */
-                                  0,              /* dwFlags           */
-                                  wideArgv[i],    /* lpWideCharStr     */
-                                  -1,             /* cchWideChar       */
-                                  strbuf,         /* lpMultiByteStr    */
-                                  sizeof(strbuf), /* cbMultiByte       */
-                                  NULL,           /* lpDefaultChar     */
-                                  NULL);          /* lpUsedDefaultChar */
-    argv[i] = _strdup(strbuf);
+    // find the required size of the buffer
+    int u8size = WideCharToMultiByte(CP_UTF8,     // CodePage
+                                     0,           // dwFlags
+                                     wideArgv[i], // lpWideCharStr
+                                     -1,          // cchWideChar
+                                     NULL,        // lpMultiByteStr
+                                     0,           // cbMultiByte
+                                     NULL,        // lpDefaultChar
+                                     NULL);       // lpUsedDefaultChar
+    if (u8size > 0) {
+      char *strbuf = (char *)malloc(u8size);
+      int ret = WideCharToMultiByte(CP_UTF8,     // CodePage
+                                    0,           // dwFlags
+                                    wideArgv[i], // lpWideCharStr
+                                    -1,          // cchWideChar
+                                    strbuf,      // lpMultiByteStr
+                                    u8size,      // cbMultiByte
+                                    NULL,        // lpDefaultChar
+                                    NULL);       // lpUsedDefaultChar
+      if (ret) {
+        argv[i] = strbuf;
+      } else {
+        argv[i] = _strdup("");
+        free(strbuf);
+      }
+    } else {
+      argv[i] = _strdup("");
+    }
   }
   argv[argc] = NULL; // required by C standard at end of list