#310 Fix warnings with mingw-w64 12

[Jason]

I tested trunk against a daily prerelease build of ubuntu 23.04, which has mingw-w64 12, and got a couple of warnings about a dangling pointer and a not ignored unused variable. So I made a patch that fixes these two issues.

[Anders]

We don't want to pass that extra parameter in so many places.

What about just static int *g_parms = 0;?

[Jason]

First thing I tried, didn't work. Here is the warning from mingw-w64:

Source/exehead/exec.c: In function 'ExecuteEntry':
Source/exehead/exec.c:274:11: warning: storing the address of local variable 'lent' in 'g_parms' [-Wdangling-pointer=]
  274 |   g_parms = lent.offsets;
      |   ~~~~~~~~^~~~~~~~~~~~~~
Source/exehead/exec.c:256:9: note: 'lent' declared here
  256 |   entry lent = *entry_;
      |         ^~~~
Source/exehead/exec.c:119:13: note: 'g_parms' declared here
  119 | static int *g_parms = 0;
      |             ^~~~~~~

Previous versions of mingw-w64 in ubuntu were based on gcc 10, but this is the first version of ubuntu (23.04) using the newer gcc 12 backend for mingw-w64.

Some research showed that other software revealed the same issues when they upgraded to gcc 12 proper.

Can we just add a define that references 'parms' indirectly and remove the global variable?

@@ -148,13 +148,14 @@
 // the string to expand gets modified.
 // When calling this function with numbers like 0x13, it means create the string
 // from the string ID found in entry.offset[3] and put it into g_bufs[1].
-static TCHAR * NSISCALL GetStringFromParm(int id_)
+static TCHAR * NSISCALL GetStringFromParmEx(const int *parms, int id_)
 {
   int id = id_ < 0 ? -id_ : id_;

-  TCHAR *result = GetNSISString(g_bufs[id >> 4], g_parms[id & 0xF]);
+  TCHAR *result = GetNSISString(g_bufs[id >> 4], parms[id & 0xF]);
   if (id_ < 0) validate_filename(result);
   return result;
 }
+#define GetStringFromParm(id_) GetStringFromParmEx(parms, id_)

[Anders]

All the functions using it are static and only called by that function so the pointer cannot dangle.

If you can't fool it with a (int*)(char*) cast then ifdef GCC pragma/attribute away the warning.

[Jason]

Alright.

Index: Contrib/Makensisw/utils.h
===================================================================
--- Contrib/Makensisw/utils.h   (revision 7387)
+++ Contrib/Makensisw/utils.h   (working copy)
@@ -84,8 +84,8 @@
 void SetDialogFocus(HWND hDlg, HWND hCtl); // Use this and not SetFocus()!
 #define DlgRet(hDlg, val) ( SetWindowLongPtr((hDlg), DWLP_MSGRESULT, (val)) | TRUE )
 HWND GetComboEdit(HWND hCB);
-#define DisableItems(hwnd) EnableDisableItems(((hwnd), 0))
-#define EnableItems(hwnd) EnableDisableItems(((hwnd), 1))
+#define DisableItems(hwnd) EnableDisableItems(((void)(hwnd), 0))
+#define EnableItems(hwnd) EnableDisableItems(((void)(hwnd), 1))
 void EnableDisableItems(int on);
 bool OpenRegSettingsKey(HKEY &hKey, bool create = false);
 #define CreateRegSettingsKey(refhkey) OpenRegSettingsKey((refhkey), true)
Index: Source/exehead/exec.c
===================================================================
--- Source/exehead/exec.c   (revision 7387)
+++ Source/exehead/exec.c   (working copy)
@@ -271,7 +271,14 @@
   //var4 = g_usrvars[parm4];
   //var5 = g_usrvars[parm5];

+#if __GNUC__ >= 12
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-pointer"
+#endif
   g_parms = lent.offsets;
+#if __GNUC__ >= 12
+#pragma GCC diagnostic pop
+#endif

   switch (which)
   {

I'll also attach an alternate patch that removes 'g_parms' and passes the parms through using defines, in case anyone else searches for this issue.