Don't call strerror or perror after fork, it's unsafe. Added safe_strerror and safe_perror replacements.

Fixes https://github.com/fish-shell/fish-shell/issues/495

1 files changed, 49 insertions, 0 deletions

diff --git a/wutil.cpp b/wutil.cpp
index 75fbac55..7d2d200d 100644
--- a/wutil.cpp
+++ b/wutil.cpp
@@ -292,6 +292,55 @@ void wperror(const wcstring &s)
     fwprintf(stderr, L"%s\n", strerror(e));
 }
 
+static inline void safe_append(char *buffer, const char *s, size_t buffsize)
+{
+    strncat(buffer, s, buffsize - strlen(buffer) - 1);
+}
+
+const char *safe_strerror(int err)
+{
+    if (err >= 0 && err < sys_nerr && sys_errlist[err] != NULL)
+    {
+        return sys_errlist[err];
+    }
+    else
+    {
+        int saved_err = errno;
+        
+        /* Use a shared buffer for this case */
+        static char buff[384];
+        char errnum_buff[64];
+        format_long_safe(errnum_buff, err);
+        
+        buff[0] = '\0';
+        safe_append(buff, "unknown error (errno was ", sizeof buff);
+        safe_append(buff, errnum_buff, sizeof buff);
+        safe_append(buff, ")", sizeof buff);
+        
+        errno = saved_err;
+        return buff;
+    }
+}
+
+void safe_perror(const char *message)
+{
+    // Note we cannot use strerror, because on Linux it uses gettext, which is not safe
+    int err = errno;
+    
+    char buff[384];
+    buff[0] = '\0';
+    
+    if (message) {
+        safe_append(buff, message, sizeof buff);
+        safe_append(buff, ": ", sizeof buff);
+    }
+    safe_append(buff, safe_strerror(err), sizeof buff);
+    safe_append(buff, "\n", sizeof buff);
+    
+    write(STDERR_FILENO, buff, strlen(buff));
+    errno = err;
+}
+
 #ifdef HAVE_REALPATH_NULL
 
 wchar_t *wrealpath(const wcstring &pathname, wchar_t *resolved_path)