diff options
| -rw-r--r-- | libio/bits/types/struct_FILE.h | 4 | ||||
| -rw-r--r-- | libio/genops.c | 26 | ||||
| -rw-r--r-- | libio/stdfiles.c | 15 |
3 files changed, 43 insertions, 2 deletions
diff --git a/libio/bits/types/struct_FILE.h b/libio/bits/types/struct_FILE.h index 7cdaae8..d8d2663 100644 --- a/libio/bits/types/struct_FILE.h +++ b/libio/bits/types/struct_FILE.h @@ -92,10 +92,10 @@ struct _IO_FILE_complete struct _IO_wide_data *_wide_data; struct _IO_FILE *_freeres_list; void *_freeres_buf; - size_t __pad5; + struct _IO_FILE **_prevchain; int _mode; /* Make sure we don't get into trouble again. */ - char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)]; + char _unused2[15 * sizeof (int) - 5 * sizeof (void *)]; }; /* These macros are used by bits/stdio.h and internal headers. */ diff --git a/libio/genops.c b/libio/genops.c index bc45e60..994ee9c 100644 --- a/libio/genops.c +++ b/libio/genops.c @@ -48,6 +48,19 @@ flush_cleanup (void *not_used) } #endif +/* Fields in struct _IO_FILE after the _lock field are internal to + glibc and opaque to applications. We can change them as long as + the size of struct _IO_FILE is unchanged, which is checked as the + part of glibc ABI with sizes of _IO_2_1_stdin_, _IO_2_1_stdout_ + and _IO_2_1_stderr_. + + NB: When _IO_vtable_offset (fp) == 0, copy relocation will cover the + whole struct _IO_FILE. Otherwise, only fields up to the _lock field + will be copied. */ +_Static_assert (offsetof (struct _IO_FILE, _prevchain) + > offsetof (struct _IO_FILE, _lock), + "offset of _prevchain > offset of _lock"); + void _IO_un_link (struct _IO_FILE_plus *fp) { @@ -62,6 +75,14 @@ _IO_un_link (struct _IO_FILE_plus *fp) #endif if (_IO_list_all == NULL) ; + else if (_IO_vtable_offset ((FILE *) fp) == 0) + { + FILE **pr = fp->file._prevchain; + FILE *nx = fp->file._chain; + *pr = nx; + if (nx != NULL) + nx->_prevchain = pr; + } else if (fp == _IO_list_all) _IO_list_all = (struct _IO_FILE_plus *) _IO_list_all->file._chain; else @@ -95,6 +116,11 @@ _IO_link_in (struct _IO_FILE_plus *fp) _IO_flockfile ((FILE *) fp); #endif fp->file._chain = (FILE *) _IO_list_all; + if (_IO_vtable_offset ((FILE *) fp) == 0) + { + fp->file._prevchain = (FILE **) &_IO_list_all; + _IO_list_all->file._prevchain = &fp->file._chain; + } _IO_list_all = fp; #ifdef _IO_MTSAFE_IO _IO_funlockfile ((FILE *) fp); diff --git a/libio/stdfiles.c b/libio/stdfiles.c index cd8eca8..12db164 100644 --- a/libio/stdfiles.c +++ b/libio/stdfiles.c @@ -54,4 +54,19 @@ DEF_STDFILE(_IO_2_1_stdout_, 1, &_IO_2_1_stdin_, _IO_NO_READS); DEF_STDFILE(_IO_2_1_stderr_, 2, &_IO_2_1_stdout_, _IO_NO_READS+_IO_UNBUFFERED); struct _IO_FILE_plus *_IO_list_all = &_IO_2_1_stderr_; + +/* Finish double-linking stdin, stdout, and stderr in a constructor. + Static initialization cannot complete the _prevchain setup. */ + +__THROW __attribute__ ((constructor)) +static void +_IO_stdfiles_init (void) +{ + struct _IO_FILE **f; + for (f = (struct _IO_FILE **) &_IO_list_all; + *f != NULL; + f = &(*f)->_chain) + (*f)->_prevchain = f; +} + libc_hidden_data_def (_IO_list_all) |