X-Git-Url: http://wien.tomnetworks.com/gitweb/?a=blobdiff_plain;f=support%2Ferrno.c;h=878e9560eb6db36d565cc35d49773d62ca7b236a;hb=a3e3afa3b6f227dba556637d3f465b4469262826;hp=a5d215513bb856426b62e00a6bf36058d7091dce;hpb=edb6779cf2c63aadcd721340152947922ec1ecb4;p=mono.git

diff --git a/support/errno.c b/support/errno.c
index a5d215513bb..878e9560eb6 100644
--- a/support/errno.c
+++ b/support/errno.c
@@ -2,11 +2,6 @@
  * <errno.h> wrapper functions.
  */
 
-/* to get XPG's strerror_r declaration */
-#undef _GNU_SOURCE
-#undef _XOPEN_SOURCE
-#define _XOPEN_SOURCE 600
-
 #include <errno.h>
 #include <string.h>
 #include "mph.h"
@@ -14,26 +9,109 @@
 
 G_BEGIN_DECLS
 
-/* DEPRECATED: Use the Stdlib version instead */
 void
-Mono_Posix_Syscall_SetLastError (int error_number)
+Mono_Posix_Stdlib_SetLastError (int error_number)
 {
 	errno = error_number;
 }
 
-void
-Mono_Posix_Stdlib_SetLastError (int error_number)
+#ifdef HAVE_STRERROR_R
+
+/* 
+ * There are two versions of strerror_r: 
+ *  - the GNU version:  char *strerror_r (int errnum, char *buf, size_t n);
+ *  - the XPG version:    int strerror_r (int errnum, char *buf, size_t n);
+ *
+ * Ideally I could stick with the XPG version, but we need to support 
+ * Red Hat 9, which only supports the GNU version.
+ *
+ * Furthermore, I do NOT want to export the GNU version in Mono.Posix.dll, 
+ * as that's supposed to contain *standard* function definitions (give or 
+ * take a few GNU extensions).  Portability trumps all.
+ *
+ * Consequently, we export the functionality of the XPG version.  
+ * Internally, we se the GNU version if _GNU_SOURCE is defined, otherwise 
+ * we assume that the XPG version is present.
+ */
+
+#ifdef _GNU_SOURCE
+#define mph_min(x,y) ((x) <= (y) ? (x) : (y))
+
+/* If you pass an invalid errno value to glibc 2.3.2's strerror_r, you get
+ * back the string "Unknown error" with the error value appended. */
+static const char mph_unknown[] = "Unknown error ";
+
+/*
+ * Translate the GNU semantics to the XPG semantics.
+ *
+ * From reading the (RH9-using) GLibc 2.3.2 sysdeps/generic/_strerror.c, 
+ * we can say the following:
+ *   - If errnum is a valid error number, a pointer to a constant string is
+ *     returned.  Thus, the prototype *lies* (it's not really a char*).
+ *     `buf' is unchanged (WTF?).
+ *   - If errnum is an *invalid* error number, an error message is copied
+ *     into `buf' and `buf' is returned.  The error message returned is
+ *     "Unknown error %i", where %i is the input errnum.
+ *
+ * Meanwhile, XPG always modifies `buf' if there's enough space, and either
+ * returns 0 (success) or -1 (error) with errno = EINVAL (bad errnum) or
+ * ERANGE (`buf' isn't big enough).  Also, GLibc 2.3.3 (which has the XPG
+ * version) first checks the validity of errnum first, then does the copy.
+ *
+ * Assuming that the GNU implementation doesn't change much (ha!), we can
+ * check for EINVAL by comparing the strerror_r return to `buf', OR by
+ * comparing the return value to "Uknown error".  (This assumes that 
+ * strerror_r will always only return the input buffer for errors.)
+ *
+ * Check for ERANGE by comparing the string length returned by strerror_r to
+ * `n'.
+ *
+ * Then pray that this actually works...
+ */
+gint32
+Mono_Posix_Syscall_strerror_r (int errnum, char *buf, mph_size_t n)
 {
-	errno = error_number;
+	char *r;
+	char ebuf [sizeof(mph_unknown)];
+	size_t len;
+	size_t blen;
+
+	mph_return_if_size_t_overflow (n);
+
+	/* first, check for valid errnum */
+	r = strerror_r (errnum, ebuf, sizeof(ebuf));
+	len = strlen (r);
+
+	if (r == ebuf ||
+			strncmp (r, mph_unknown, mph_min (len, sizeof(mph_unknown))) == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/* valid errnum (we hope); is buffer big enough? */
+	blen = (size_t) n;
+	if ((len+1) > blen) {
+		errno = ERANGE;
+		return -1;
+	}
+
+	strncpy (buf, r, len);
+	buf[len] = '\0';
+
+	return 0;
 }
 
-#ifdef HAVE_STRERROR_R
+#else /* !def _GNU_SOURCE */
+
 gint32
 Mono_Posix_Syscall_strerror_r (int errnum, char *buf, mph_size_t n)
 {
 	mph_return_if_size_t_overflow (n);
 	return strerror_r (errnum, buf, (size_t) n);
 }
+
+#endif /* def _GNU_SOURCE */
+
 #endif /* def HAVE_STRERROR_R */
 
 G_END_DECLS