Merge pull request #2250 from esdrubal/master

[mono.git] / support / errno.c

diff --git a/support/errno.c b/support/errno.c
index fbdac433ef53dd6ed29b176c83e01577498f6de2..74c2fdf5648bd0613f87d8cb93b41431e1481e2d 100644 (file)
--- a/support/errno.c
+++ b/support/errno.c
@@ -2,31 +2,137 @@
  * <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 "map.h"
 #include "mph.h"
 #include <stdio.h>
 
 G_BEGIN_DECLS
 
 void
-Mono_Posix_Syscall_SetLastError (int error_number)
+Mono_Posix_Stdlib_SetLastError (int error_number)
 {
        errno = 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)
+{
+       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 */
+#if PLATFORM_ANDROID
+       /* Android NDK defines _GNU_SOURCE but strerror_r follows the XSI semantics
+        * not the GNU one. XSI version returns an integer, as opposed to the GNU one
+        * which returns pointer to the buffer.
+        */
+       if (strerror_r (errnum, ebuf, sizeof(ebuf)) == -1) {
+               /* XSI strerror_r will return -1 if errno is set, but if we leave the value
+                * alone it breaks Mono.Posix StdioFileStream tests, so we'll ignore the value
+                * and set errno as below
+                */
+               errno = EINVAL;
+               return -1;
+       }
+       r = ebuf;
+#else
+       r = strerror_r (errnum, ebuf, sizeof(ebuf));
+#endif
+       if (!r) {
+               errno = EINVAL;
+               return -1;
+       } 
+       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;
+}
+
+#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