Favor strerror_s and fopen_s on MSVC

Make remaining calls to fopen and strerror use strerror_s and fopen_s
on MSVC.

ChangeLog

@@ -1,5 +1,9 @@
 2013-02-28  Jay Berkenbilt  <ejb@ql.org>
 
+	* Favor fopen_s and strerror_s on MSVC to avoid CRT security
+	warnings.  This is useful for people who may want to use qpdf in
+	an application that is Windows 8 certified.
+
 	* New method QUtil::safe_fopen to wrap calls to fopen.  This is
 	less cumbersome than calling QUtil::fopen_wrapper.
 

libqpdf/QUtil.cc

@@ -96,7 +96,22 @@ QUtil::unsigned_char_pointer(char const* str)
 void
 QUtil::throw_system_error(std::string const& description)
 {
-    throw std::runtime_error(description + ": " + strerror(errno)); // XXXX
+#ifdef _MSC_VER
+    // "94" is mentioned in the MSVC docs, but it's still safe if the
+    // message is longer.  strerror_s is a templated function that
+    // knows the size of buf and truncates.
+    char buf[94];
+    if (strerror_s(buf, errno) != 0)
+    {
+        throw std::runtime_error(description + ": failed with an unknown error");
+    }
+    else
+    {
+        throw std::runtime_error(description + ": " + buf);
+    }
+#else
+    throw std::runtime_error(description + ": " + strerror(errno));
+#endif
 }
 
 int
@@ -112,8 +127,18 @@ QUtil::os_wrapper(std::string const& description, int status)
 FILE*
 QUtil::safe_fopen(char const* filename, char const* mode)
 {
-    return fopen_wrapper(std::string("open ") + filename,
-                         fopen(filename, mode)); // XXXX
+    FILE* f = 0;
+#ifdef _MSC_VER
+    errno_t err = fopen_s(&f, filename, mode);
+    if (err != 0)
+    {
+        errno = err;
+        throw_system_error(std::string("open ") + filename);
+    }
+#else
+    f = fopen_wrapper(std::string("open ") + filename, fopen(filename, mode));
+#endif
+    return f;
 }
 
 FILE*

qpdf/qpdf-ctest.c

@@ -10,13 +10,27 @@ static qpdf_data qpdf = 0;
 
 static FILE* safe_fopen(char const* filename, char const* mode)
 {
-    FILE* f = fopen(filename, mode); /* XXXX */
+    // This function is basically a "C" port of QUtil::safe_fopen.
+    FILE* f = 0;
+#ifdef _MSC_VER
+    errno_t err = fopen_s(&f, filename, mode);
+    if (err != 0)
+    {
+        char buf[94];
+        strerror_s(buf, sizeof(buf), errno);
+	fprintf(stderr, "%s: unable to open %s: %s\n",
+		whoami, filename, buf);
+	exit(2);
+    }
+#else
+    f = fopen(filename, mode);
     if (f == NULL)
     {
 	fprintf(stderr, "%s: unable to open %s: %s\n",
-		whoami, filename, strerror(errno)); /* XXXX */
+		whoami, filename, strerror(errno));
 	exit(2);
     }
+#endif
     return f;
 }