bug#38794: 26.1; Warnings in w32 build

bug#38794: 26.1; Warnings in w32 build

[Cecilio Pardo]

Severity: wishlist
Tags: patch

I am getting some warnings building with mingw64, using gcc 9.2.0. It
complies about possible buffer overruns with sprintf. Maybe upgrade to snprintf?

This is the warnings message:

addpm.c: In function 'main':
addpm.c:291:37: warning: '\bin\' directive writing 5 bytes into a region of size between 2 and 261 [-Wformat-overflow=]
  291 |        sprintf (full_emacs_path, "%s\\bin\\%s", emacs_path, prog_name);
      |                                     ^~~~~~~
addpm.c:291:8: note: 'sprintf' output between 18 and 277 bytes into a destination of size 261
  291 |        sprintf (full_emacs_path, "%s\\bin\\%s", emacs_path, prog_name);
      |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


diff --git a/nt/addpm.c b/nt/addpm.c
index 3fd1b1bdc0..7da1fb5424 100644
--- a/nt/addpm.c
+++ b/nt/addpm.c
@@ -257,7 +257,7 @@ main (int argc, char *argv[])
 	      char full_emacs_path[MAX_PATH + 1];
 	      IPersistFile *lnk;
 	      strcat (start_folder, "\\Emacs.lnk");
-	      sprintf (full_emacs_path, "%s\\bin\\%s", emacs_path, prog_name);
+	      snprintf (full_emacs_path, sizeof (full_emacs_path), "%s\\bin\\%s", emacs_path, prog_name);
 	      IShellLinkA_SetPath (shortcut, full_emacs_path);
 	      IShellLinkA_SetDescription (shortcut, "GNU Emacs");
 	      result = IShellLinkA_QueryInterface (shortcut, &IID_IPersistFile,
@@ -288,7 +288,7 @@ main (int argc, char *argv[])
 	      char full_emacs_path[MAX_PATH + 1];
 	      IPersistFile *lnk;
 	      strcat (start_folder, "\\Emacs.lnk");
-	      sprintf (full_emacs_path, "%s\\bin\\%s", emacs_path, prog_name);
+	      snprintf (full_emacs_path, sizeof (full_emacs_path), "%s\\bin\\%s", emacs_path, prog_name);
 	      IShellLinkA_SetPath (shortcut, full_emacs_path);
 	      IShellLinkA_SetDescription (shortcut, "GNU Emacs");
 	      result = IShellLinkA_QueryInterface (shortcut, &IID_IPersistFile,




-- 
Cecilio Pardo

bug#38794: 26.1; Warnings in w32 build

[Eli Zaretskii]

tags 38794 wontfix
close 38794
thanks

> From: Cecilio Pardo <cpardo@imayhem.com>
> Date: Sun, 29 Dec 2019 17:04:41 +0100
> 
> I am getting some warnings building with mingw64, using gcc 9.2.0. It
> complies about possible buffer overruns with sprintf. Maybe upgrade to snprintf?
> 
> This is the warnings message:
> 
> addpm.c: In function 'main':
> addpm.c:291:37: warning: '\bin\' directive writing 5 bytes into a region of size between 2 and 261 [-Wformat-overflow=]
>   291 |        sprintf (full_emacs_path, "%s\\bin\\%s", emacs_path, prog_name);
>       |                                     ^~~~~~~
> addpm.c:291:8: note: 'sprintf' output between 18 and 277 bytes into a destination of size 261
>   291 |        sprintf (full_emacs_path, "%s\\bin\\%s", emacs_path, prog_name);
>       |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

They are bogus, obviously, and we would like to deprecate and remove
addpm at some future point.  So I see no reason to make it compile
cleanly with GCC's too radical warning options.

So I'm closing this bug report.

Thank you anyway for your interest in Emacs and for providing a patch.