77a6bf8489
This loop was using the number of bytes read from the file as condition
to keep reading.
From Linux's fread(3) man page:
> On success, fread() and fwrite() return the number of items read or
> written. This number equals the number of bytes transferred only when
> size is 1. If an error occurs, or the end of the file is reached, the
> return value is a short item count (or zero).
>
> The file position indicator for the stream is advanced by the number
> of bytes successfully read or written.
>
> fread() does not distinguish between end-of-file and error, and
> callers must use feof(3) and ferror(3) to determine which occurred.
This means that nread!=0 doesn't make much sense as an end condition for
the loop: nread==0 doesn't necessarily mean that EOF has been reached or
an error has occured (but that is usually the case) and nread!=0 doesn't
necessarily mean that EOF has not been reached or that no read errors
have occured. feof(3) and ferror(3) should be uses when using fread(3).
Currently curl has to performs an extra fread(3) call to get a return
value equal to 0 to stop looping.
This usually "works" (even though nread==0 shouldn't be interpreted as
EOF) if stdin is a pipe because EOF usually marks the "real" end of the
stream, so the extra fread(3) call will return immediately and the extra
read syscall won't be noticeable:
bash-5.1$ strace -e read curl -s -F file=@- 0x0.st <<< a 2>&1 |
> tail -n 5
read(0, "a\n", 4096) = 2
read(0, "", 4096) = 0
read(0, "", 4096) = 0
http://0x0.st/oRs.txt
+++ exited with 0 +++
bash-5.1$
But this doesn't work if curl is reading from stdin, stdin is a
terminal, and the EOF is being emulated using a shell with ^D. Two
consecutive ^D will be required in this case to actually make curl stop
reading:
bash-5.1$ curl -F file=@- 0x0.st
a
^D^D
http://0x0.st/oRs.txt
bash-5.1$
A possible workaround to this issue is to use a program that handles EOF
correctly to indirectly send data to curl's stdin:
bash-5.1$ cat - | curl -F file=@- 0x0.st
a
^D
http://0x0.st/oRs.txt
bash-5.1$
This patch makes curl handle EOF properly when using fread(3) in
file2memory() so that the workaround is not necessary.
Since curl was previously ignoring read errors caused by this fread(3),
ferror(3) is also used in the condition of the loop: read errors and EOF
will have the same meaning; this is done to somewhat preserve the old
behaviour instead of making the command fail when a read error occurs.
Closes #8701
|
||
|---|---|---|
| .circleci | ||
| .github | ||
| .lift | ||
| CMake | ||
| docs | ||
| include | ||
| lib | ||
| m4 | ||
| packages | ||
| plan9 | ||
| projects | ||
| scripts | ||
| src | ||
| tests | ||
| winbuild | ||
| zuul.d | ||
| .azure-pipelines.yml | ||
| .cirrus.yml | ||
| .dcignore | ||
| .dir-locals.el | ||
| .gitattributes | ||
| .gitignore | ||
| .lgtm.yml | ||
| .mailmap | ||
| acinclude.m4 | ||
| appveyor.yml | ||
| buildconf | ||
| buildconf.bat | ||
| CHANGES | ||
| CMakeLists.txt | ||
| configure.ac | ||
| COPYING | ||
| curl-config.in | ||
| GIT-INFO | ||
| libcurl.pc.in | ||
| MacOSX-Framework | ||
| Makefile.am | ||
| Makefile.dist | ||
| maketgz | ||
| mlc_config.json | ||
| README | ||
| README.md | ||
| RELEASE-NOTES | ||
| SECURITY.md | ||
Curl is a command-line tool for transferring data specified with URL syntax. Find out how to use curl by reading the curl.1 man page or the MANUAL document. Find out how to install Curl by reading the INSTALL document.
libcurl is the library curl is using to do its job. It is readily available to be used by your software. Read the libcurl.3 man page to learn how.
You can find answers to the most frequent questions we get in the FAQ document.
Study the COPYING file for distribution terms.
Contact
If you have problems, questions, ideas or suggestions, please contact us by posting to a suitable mailing list.
All contributors to the project are listed in the THANKS document.
Commercial support
For commercial support, maybe private and dedicated help with your problems or applications using (lib)curl visit the support page.
Website
Visit the curl website for the latest news and downloads.
Git
To download the latest source from the Git server do this:
git clone https://github.com/curl/curl.git
(you will get a directory named curl created, filled with the source code)
Security problems
Report suspected security problems via our HackerOne page and not in public!
Notice
Curl contains pieces of source code that is Copyright (c) 1998, 1999 Kungliga Tekniska Högskolan. This notice is included here to comply with the distribution terms.
Backers
Thank you to all our backers! 🙏 [Become a backer]
Sponsors
Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [Become a sponsor]
