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<title>[136398] trunk/base/src/darwintracelib1.0/darwintrace.c</title>
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<dt>Revision</dt> <dd><a href="https://trac.macports.org/changeset/136398">136398</a></dd>
<dt>Author</dt> <dd>cal@macports.org</dd>
<dt>Date</dt> <dd>2015-05-15 15:46:22 -0700 (Fri, 15 May 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>base: darwintrace: don't use fread(3) and fwrite(3)
fread(3) and fwrite(3) can both be interrupted by signals, return a short
read/write or error and set errno=EINTR. Since there is no way to find out
whether the interrupted call has already read or written partial data, these
calls can never be re-called correctly without possible corruption. This is
a fundamental problem in the API and the implementation on OS X.
To avoid this, use write(2) and read(2) instead.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkbasesrcdarwintracelib10darwintracec">trunk/base/src/darwintracelib1.0/darwintrace.c</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkbasesrcdarwintracelib10darwintracec"></a>
<div class="modfile"><h4>Modified: trunk/base/src/darwintracelib1.0/darwintrace.c (136397 => 136398)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/base/src/darwintracelib1.0/darwintrace.c 2015-05-15 21:10:01 UTC (rev 136397)
+++ trunk/base/src/darwintracelib1.0/darwintrace.c 2015-05-15 22:46:22 UTC (rev 136398)
</span><span class="lines">@@ -498,14 +498,30 @@
</span><span class="cx"> * \param[in] size number of bytes to read from the socket
</span><span class="cx"> */
</span><span class="cx"> static void frecv(void *restrict buf, size_t size) {
</span><del>- FILE *stream = __darwintrace_sock();
- if (1 != fread(buf, size, 1, stream)) {
- if (ferror(stream)) {
- perror("darwintrace: fread");
- } else {
- fprintf(stderr, "darwintrace: fread: end-of-file\n");
</del><ins>+ /* We cannot safely use fread(3) here, because we're not in control of the
+ * application's signal handling settings (which means we must assume
+ * SA_RESTART isn't set) and fread(3) may return short without giving us
+ * a way to know how many bytes have actually been read, i.e. without a way
+ * to do the call again. Because of this great API design and
+ * implementation on OS X, we'll just use read(2) here. */
+ int fd = fileno(__darwintrace_sock());
+ size_t count = 0;
+ while (count < size) {
+ ssize_t res = read(fd, buf + count, size - count);
+ if (res < 0) {
+ if (errno == EINTR) {
+ continue;
+ }
+ perror("darwintrace: read");
+ abort();
</ins><span class="cx"> }
</span><del>- abort();
</del><ins>+
+ if (res == 0) {
+ fprintf(stderr, "darwintrace: read: end-of-file\n");
+ abort();
+ }
+
+ count += res;
</ins><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -517,16 +533,26 @@
</span><span class="cx"> * \param[in] size number of bytes in the buffer
</span><span class="cx"> */
</span><span class="cx"> static void fsend(const void *restrict buf, size_t size) {
</span><del>- FILE *stream = __darwintrace_sock();
- if (1 != fwrite(buf, size, 1, stream)) {
- if (ferror(stream)) {
- perror("darwintrace: fwrite");
- } else {
- fprintf(stderr, "darwintrace: fwrite: end-of-file\n");
</del><ins>+ /* We cannot safely use fwrite(3) here, because we're not in control of the
+ * application's signal handling settings (which means we must assume
+ * SA_RESTART isn't set) and fwrite(3) may return short without giving us
+ * a way to know how many bytes have actually been written, i.e. without
+ * a way to do the call again. Because of this great API design and
+ * implementation on OS X, we'll just use write(2) here. */
+ int fd = fileno(__darwintrace_sock());
+ size_t count = 0;
+ while (count < size) {
+ ssize_t res = write(fd, buf + count, size - count);
+ if (res < 0) {
+ if (errno == EINTR) {
+ continue;
+ }
+ perror("darwintrace: write");
+ abort();
</ins><span class="cx"> }
</span><del>- abort();
</del><ins>+
+ count += res;
</ins><span class="cx"> }
</span><del>- fflush(stream);
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> /**
</span></span></pre>
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