From 1afd22ef2289241f27e291d9fe6709a46b859caa Mon Sep 17 00:00:00 2001
From: doomfrawen <doomfrawen@users.noreply.github.com>
Date: Sun, 9 Aug 2026 09:24:59 -0700
Subject: [PATCH] Fix Windows/MinGW build: missing err.h, uninitialized pointer
 in stdlib.c

- src/nfc-utils.h/.c and src/windows.h include <err.h>, a BSD/glibc-only
  header not shipped by MinGW-w64, so the GNU-toolchain build (autoreconf
  + gcc, as opposed to the VS2019/clang-cl path this repo also supports)
  fails with 'err.h: No such file or directory'. windows.h doesn't call
  anything from it, so that include is simply dropped. nfc-utils.h's
  DBG/WARN/ERR macros do use warnx(), so on _WIN32 this adds a small
  static inline warnx() shim instead of the header, and drops the
  redundant second #include <err.h> in nfc-utils.c.

- src/stdlib.c's setenv()/unsetenv() declare 'char *str[32]' (an array
  of 32 uninitialized pointers) and then do strcpy(*str, name) etc,
  which dereferences the first (uninitialized/garbage) pointer in that
  array and writes through it - undefined behavior, not just a
  compile-time type mismatch. Changed to 'char str[32]' (an actual
  32-byte buffer) and dropped the erroneous dereferences.
---
 src/nfc-utils.c |  1 -
 src/nfc-utils.h | 15 ++++++++++++++-
 src/stdlib.c    | 18 +++++++++---------
 src/windows.h   |  1 -
 4 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/nfc-utils.c b/src/nfc-utils.c
index 5c0a264..f5b13b1 100644
--- a/src/nfc-utils.c
+++ b/src/nfc-utils.c
@@ -37,7 +37,6 @@
  * @brief Provide some examples shared functions like print, parity calculation, options parsing.
  */
 #include <nfc/nfc.h>
-#include <err.h>
 
 #include "nfc-utils.h"
 
diff --git a/src/nfc-utils.h b/src/nfc-utils.h
index a0a599e..b46b019 100644
--- a/src/nfc-utils.h
+++ b/src/nfc-utils.h
@@ -43,7 +43,20 @@
 
 #  include <stdlib.h>
 #  include <string.h>
-#  include <err.h>
+#  ifdef _WIN32
+#    include <stdio.h>
+#    include <stdarg.h>
+static inline void warnx(const char *fmt, ...)
+{
+  va_list ap;
+  va_start(ap, fmt);
+  vfprintf(stderr, fmt, ap);
+  va_end(ap);
+  fprintf(stderr, "\n");
+}
+#  else
+#    include <err.h>
+#  endif
 #  include <nfc/nfc-types.h>
 
 /**
diff --git a/src/stdlib.c b/src/stdlib.c
index 9a0a512..0dfa02f 100644
--- a/src/stdlib.c
+++ b/src/stdlib.c
@@ -40,19 +40,19 @@ int setenv(const char *name, const char *value, int overwrite)
 {
   char *env = getenv(name);
   if ((env && overwrite) || (!env)) {
-    char *str[32];
-    strcpy(*str, name);
-    strcat(*str, "=");
-    strcat(*str, value);
-    return _putenv(*str);
+    char str[32];
+    strcpy(str, name);
+    strcat(str, "=");
+    strcat(str, value);
+    return _putenv(str);
   }
   return -1;
 }
 
 void unsetenv(const char *name)
 {
-  char *str[32];
-  strcpy(*str, name);
-  strcat(*str, "=");
-  _putenv(*str);
+  char str[32];
+  strcpy(str, name);
+  strcat(str, "=");
+  _putenv(str);
 }
diff --git a/src/windows.h b/src/windows.h
index 2a9e722..134ca99 100644
--- a/src/windows.h
+++ b/src/windows.h
@@ -35,7 +35,6 @@
 
 #  include <windows.h>
 #  include <winerror.h>
-#  include <err.h>
 #  if defined (__MINGW32__)
 /*
  * Cheating here on the snprintf to incorporate the format argument