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author | Zack Weinberg <zackw@panix.com> | 2018-02-21 19:12:51 -0500 |
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committer | Zack Weinberg <zackw@panix.com> | 2018-03-13 08:31:56 -0400 |
commit | 2cc7bad0ae0a412e75270be5ed41d45c03e7a931 (patch) | |
tree | a726dff1dc98e5fabf47685d10f9c681265db95b /libio/Makefile | |
parent | 778f1974863d63e858b6d0105e41d6f0c30732d3 (diff) | |
download | glibc-2cc7bad0ae0a412e75270be5ed41d45c03e7a931.zip glibc-2cc7bad0ae0a412e75270be5ed41d45c03e7a931.tar.gz glibc-2cc7bad0ae0a412e75270be5ed41d45c03e7a931.tar.bz2 |
[BZ 1190] Make EOF sticky in stdio.
C99 specifies that the EOF condition on a file is "sticky": once EOF
has been encountered, all subsequent reads should continue to return
EOF until the file is closed or something clears the "end-of-file
indicator" (e.g. fseek, clearerr). This is arguably a change from
C89, where the wording was ambiguous; the BSDs always had sticky EOF,
but the System V lineage would attempt to read from the underlying fd
again. GNU libc has followed System V for as long as we've been
using libio, but nowadays C99 conformance and BSD compatibility are
more important than System V compatibility.
You might wonder if changing the _underflow impls is sufficient to
apply the C99 semantics to all of the many stdio functions that
perform input. It should be enough to cover all paths to _IO_SYSREAD,
and the only other functions that call _IO_SYSREAD are the _seekoff
impls, which is OK because seeking clears EOF, and the _xsgetn impls,
which, as far as I can tell, are unused within glibc.
The test programs in this patch use a pseudoterminal to set up the
necessary conditions. To facilitate this I added a new test-support
function that sets up a pair of pty file descriptors for you; it's
almost the same as BSD openpty, the only differences are that it
allocates the optionally-returned tty pathname with malloc, and that
it crashes if anything goes wrong.
[BZ #1190]
[BZ #19476]
* libio/fileops.c (_IO_new_file_underflow): Return EOF immediately
if the _IO_EOF_SEEN bit is already set; update commentary.
* libio/oldfileops.c (_IO_old_file_underflow): Likewise.
* libio/wfileops.c (_IO_wfile_underflow): Likewise.
* support/support_openpty.c, support/tty.h: New files.
* support/Makefile (libsupport-routines): Add support_openpty.
* libio/tst-fgetc-after-eof.c, wcsmbs/test-fgetwc-after-eof.c:
New test cases.
* libio/Makefile (tests): Add tst-fgetc-after-eof.
* wcsmbs/Makefile (tests): Add tst-fgetwc-after-eof.
Diffstat (limited to 'libio/Makefile')
-rw-r--r-- | libio/Makefile | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/libio/Makefile b/libio/Makefile index 3e08ed0..cbe14a8 100644 --- a/libio/Makefile +++ b/libio/Makefile @@ -64,7 +64,8 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc \ bug-memstream1 bug-wmemstream1 \ tst-setvbuf1 tst-popen1 tst-fgetwc bug-wsetpos tst-fseek \ tst-fwrite-error tst-ftell-partial-wide tst-ftell-active-handler \ - tst-ftell-append tst-fputws tst-bz22415 + tst-ftell-append tst-fputws tst-bz22415 tst-fgetc-after-eof + ifeq (yes,$(build-shared)) # Add test-fopenloc only if shared library is enabled since it depends on # shared localedata objects. |