In doc examples, don't ignore read/write results

[mbrubeck]

Calling Read::read or Write::write without checking the returned usize value is almost always an error. Example code in the documentation should demonstrate how to use the return value correctly. Otherwise, people might copy the example code thinking that it is okay to "fire and forget" these methods.

[rust-highfive]

r? @bluss

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[Centril]

r? @Centril -- r=me rollup with green travis.

[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:00059ed4:start=1553877351100236139,finish=1553877352281280019,duration=1181043880
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
Setting environment variables from .travis.yml
---
travis_time:start:test_assembly
Check compiletest suite=assembly mode=assembly (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
[01:26:25] 
[01:26:25] running 9 tests
[01:26:25] iiiiiiiii
[01:26:25] 
[01:26:25]  finished in 0.173
[01:26:25] travis_fold:end:test_assembly

---
travis_time:start:test_debuginfo
Check compiletest suite=debuginfo mode=debuginfo-both (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
[01:26:42] 
[01:26:42] running 120 tests
[01:27:12] .iiiii...i.....i..i...i..i.i...i.ii...i.....i..i....i..........iiii..........i...ii...i.......ii.i.i 100/120
[01:27:18] .i......iii.i.....ii
[01:27:18] 
[01:27:18]  finished in 36.026
[01:27:18] travis_fold:end:test_debuginfo

---
[01:56:23] travis_fold:end:stage0-linkchecker

[01:56:23] travis_time:end:stage0-linkchecker:start=1553884343946150840,finish=1553884346142709293,duration=2196558453

[01:56:25] std/io/trait.Write.html:44: broken link fragment `#tymethod.write_all` pointing to `std/io/trait.Write.html`
[01:56:35] thread 'main' panicked at 'found some broken links', src/tools/linkchecker/main.rs:41:9
[01:56:35] 
[01:56:35] 
[01:56:35] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/linkchecker" "/checkout/obj/build/x86_64-unknown-linux-gnu/doc"
[01:56:35] expected success, got: exit code: 101
[01:56:35] expected success, got: exit code: 101
[01:56:35] 
[01:56:35] 
[01:56:35] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:56:35] Build completed unsuccessfully in 0:43:22
[01:56:35] make: *** [check] Error 1
[01:56:35] Makefile:48: recipe for target 'check' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:01997a6c
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Fri Mar 29 18:32:38 UTC 2019
---
travis_time:end:0be56177:start=1553884361204163116,finish=1553884361210860453,duration=6697337
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:012f200a
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:08b0df52
travis_time:start:08b0df52
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:08f1485a
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Centril]

@bors r+ rollup

[bors]

📌 Commit b6fb3e3 has been approved by Centril