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Consistently save errno immediately after the operation setting it

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Prevent the situation where errno is set by function A, then function B
is called (which is typically _(), but could be anything else) and it
overwrites errno, then errno is checked by the caller.

errno is a horrific API, and we need to be careful to save its value as
soon as a function call (which might set it) returns. i.e. Follow the
pattern:
  int errsv, ret;
  ret = some_call_which_might_set_errno ();
  errsv = errno;

  if (ret < 0)
    puts (strerror (errsv));

This patch implements that pattern throughout GLib. There might be a few
places in the test code which still use errno directly. They should be
ported as necessary. It doesn’t modify all the call sites like this:
  if (some_call_which_might_set_errno () && errno == ESOMETHING)
since the refactoring involved is probably more harmful than beneficial
there. It does, however, refactor other call sites regardless of whether
they were originally buggy.

https://bugzilla.gnome.org/show_bug.cgi?id=785577
This commit is contained in:
Philip Withnall
2017-07-31 11:30:55 +01:00
parent 41a4a70b43
commit 5cddde1fb2
44 changed files with 337 additions and 166 deletions
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16
gio/glocalfileoutputstream.c
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@@ -748,6 +748,7 @@ handle_overwrite_open (const char *filename,
int open_flags;
int res;
int mode;
int errsv;
mode = mode_from_flags_or_info (flags, reference_info);
@@ -763,12 +764,13 @@ handle_overwrite_open (const char *filename,
#ifdef O_NOFOLLOW
is_symlink = FALSE;
fd = g_open (filename, open_flags | O_NOFOLLOW, mode);
errsv = errno;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
if (fd == -1 && errno == EMLINK)
if (fd == -1 && errsv == EMLINK)
#elif defined(__NetBSD__)
if (fd == -1 && errno == EFTYPE)
if (fd == -1 && errsv == EFTYPE)
#else
if (fd == -1 && errno == ELOOP)
if (fd == -1 && errsv == ELOOP)
#endif
{
/* Could be a symlink, or it could be a regular ELOOP error,
@@ -778,13 +780,13 @@ handle_overwrite_open (const char *filename,
}
#else
fd = g_open (filename, open_flags, mode);
errsv = errno;
/* This is racy, but we do it as soon as possible to minimize the race */
is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
#endif
if (fd == -1)
{
int errsv = errno;
char *display_name = g_filename_display_name (filename);
g_set_error (error, G_IO_ERROR,
g_io_error_from_errno (errsv),
@@ -799,10 +801,10 @@ handle_overwrite_open (const char *filename,
#else
res = fstat (fd, &original_stat);
#endif
errsv = errno;
if (res != 0)
if (res != 0)
{
int errsv = errno;
char *display_name = g_filename_display_name (filename);
g_set_error (error, G_IO_ERROR,
g_io_error_from_errno (errsv),