For certain APIs, the return value of the function does not distinguish
between failure (which populates errno) and other non-error conditions
(which do not set errno).
For example, `fgets` returns `NULL` both when an error has occurred, or
upon EOF. If `errno` is already `EINTR` for whatever reason, then
```
RetryAfterSignal(nullptr, fgets, ...);
```
on a stream that has reached EOF would infinite loop.
Fix this by setting `errno` to `0` before each attempt in
`RetryAfterSignal`.
Patch by Ricky Zhou!
Differential Revision: https://reviews.llvm.org/D48755
llvm-svn: 336479
The difference from the previous version is the use of decltype, as the
implementation of std::result_of in libc++ did not work correctly for
variadic function like open(2).
Original summary:
This function retries an operation if it was interrupted by a signal
(failed with EINTR). It's inspired by the TEMP_FAILURE_RETRY macro in
glibc, but I've turned that into a template function. I've also added a
fail-value argument, to enable the function to be used with e.g.
fopen(3), which is documented to fail for any reason that open(2) can
fail (which includes EINTR).
The main user of this function will be lldb, but there were also a
couple of uses within llvm that I could simplify using this function.
Reviewers: zturner, silvas, joerg
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D33895
llvm-svn: 306671
The fix in r306003 uncovered a pretty fundamental problem that libc++
implementation of std::result_of does not handle the prototype of
open(2) correctly (presumably because it contains ...). This makes the
whole function unusable in its current form, so I am also reverting the
original commit (r305892), which introduced the function, at least until
I figure out a way to solve the libc++ issue.
llvm-svn: 306005
The default value of the ResultT template argument (which was there only
to avoid spelling out the long std::result_of template multiple times)
was being overriden by function call template argument deduction. This
manifested itself as a compiler error when calling the function as
FILE *X = RetryAfterSignal(nullptr, fopen, ...)
because the function would try to assign the result of fopen to
nullptr_t, but a more insidious side effect was that
RetryAfterSignal(-1, read, ...) would return "int" instead of "ssize_t",
losing precision along the way.
I fix this by having the function take the argument in a way that
prevents argument deduction from kicking in and add a test that makes
sure the return type is correct.
llvm-svn: 306003
Summary:
This function retries an operation if it was interrupted by a signal
(failed with EINTR). It's inspired by the TEMP_FAILURE_RETRY macro in
glibc, but I've turned that into a template function. I've also added a
fail-value argument, to enable the function to be used with e.g.
fopen(3), which is documented to fail for any reason that open(2) can
fail (which includes EINTR).
The main user of this function will be lldb, but there were also a
couple of uses within llvm that I could simplify using this function.
Reviewers: zturner, silvas, joerg
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D33895
llvm-svn: 305892
Chandler Carruth