feat(libacron): complete Win32 error message formatting

The former approach, strerror(3), is not working on Win32 errors (GetLastError()) or WinSock errors (WSAGetLastError()).

Signed-off-by: Trumeet <yuuta@yuuta.moe>

3 files changed, 40 insertions, 2 deletions

diff --git a/client/libacron/library.c b/client/libacron/library.c
index c014ed9..e2ee872 100644
--- a/client/libacron/library.c
+++ b/client/libacron/library.c
@@ -42,5 +42,6 @@ int ac_free(void) {
     }
     free(config);
     config = NULL;
+    helpers_cleanup();
     return AC_E_OK;
 }
\ No newline at end of file
diff --git a/client/libacron/private/helpers.c b/client/libacron/private/helpers.c
index 5a23e34..0cb452b 100644
--- a/client/libacron/private/helpers.c
+++ b/client/libacron/private/helpers.c
@@ -12,6 +12,10 @@
 #include <errno.h>
 #include <stdio.h>
 
+#ifdef WIN32
+#include <windows.h>
+#endif
+
 int alloc(void *existing,
             unsigned int count,
             unsigned int bytes,
@@ -49,17 +53,45 @@ int strdup2(const char *str, char **out) {
     return AC_E_OK;
 }
 
+#ifdef WIN32
+static _Thread_local LPTSTR err_buf = NULL;
+#else
 static _Thread_local char err_buf[1024];
+#endif
 
 char *strerror2(int errnum) {
 #ifdef WIN32
-    /* Win32 strerror(3) is thread-safe. */
-    return strerror(errnum);
+    if (err_buf) {
+        LocalFree(err_buf);
+        err_buf = NULL;
+    }
+    FormatMessage(
+            FORMAT_MESSAGE_FROM_SYSTEM |
+            FORMAT_MESSAGE_ALLOCATE_BUFFER |
+            FORMAT_MESSAGE_IGNORE_INSERTS,
+            NULL,
+            errnum,
+            MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+            (LPTSTR) &err_buf,
+            0,
+            NULL);
+    if (!err_buf) {
+        return "Unknown error";
+    }
 #else
     int r;
     if ((r = strerror_r(errnum, err_buf, sizeof(err_buf) / sizeof(char)))) {
         snprintf(err_buf, 1024, "%d (%d)", errnum, r);
     }
+#endif
     return err_buf;
+}
+
+void helpers_cleanup(void) {
+#ifdef WIN32
+    if (err_buf) {
+        LocalFree(err_buf);
+        err_buf = NULL;
+    }
 #endif
 }
\ No newline at end of file
diff --git a/client/libacron/private/helpers.h b/client/libacron/private/helpers.h
index f1635a6..c6500b8 100644
--- a/client/libacron/private/helpers.h
+++ b/client/libacron/private/helpers.h
@@ -42,4 +42,9 @@ int strdup2(const char *str, char **out);
  */
 char *strerror2(int errnum);
 
+/**
+ * Cleanup any necessary memory during exit of the current thread.
+ */
+void helpers_cleanup(void);
+
 #endif /* LIBAC_HELPERS_H */