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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - String truncation with buffer_ostream and addPassesToEmitFile"
href="https://llvm.org/bugs/show_bug.cgi?id=25272">25272</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>String truncation with buffer_ostream and addPassesToEmitFile
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>3.7
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tim.besard@elis.ugent.be
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15132" name="attach_15132" title="testcase.cpp">attachment 15132</a> <a href="attachment.cgi?id=15132&action=edit" title="testcase.cpp">[details]</a></span>
testcase.cpp
Hi,
I have some code which compiles to an in-memory buffer by wrapping an
std::string with an raw_string_ostream and passing it to addPassesToEmitFile.
This used to work fine on LLVM 3.5, after wrapping the raw_string_ostream with
a formatted_raw_ostream. LLVM 3.7 has changed the interface, requiring a
pwrite-able buffer instead. Looking at the raw_pwrite_stream class hierarchy, I
decided to wrap the raw_string_ostream with a buffer_ostream. This however
yields truncated output (at a seemingly random spot)...
Attached is a relatively large, but straightforward test-case (parse, compile,
emit). Compile it with: clang++ -std=c++11 test.cpp $(llvm-config -cxxflags
--system-libs --libs all) -L$(llvm-config --libdir) -o test
The test-case works on both LLVM 3.7 and 3.5, by means of #ifdef's.
Output on 3.5:
//
// Generated by LLVM NVPTX Back-End
//
.version 3.2
.target sm_20
.address_size 32
// .globl dummy
.visible .entry dummy(
)
{
ret;
}
Output on 3.7:
//
// Generated by LLVM NVPTX Back-End
//
.version 3.2
.target sm_20
.address_size 32
// .globl dummy
.visible .entry dummy(
I tried compiling with ASAN / running with valgrind, but no errors were
revealed. Strangely, deleting the PassManager (currently commented) fixes the
output! So I'm still thinking it could be a memory error.
I also suspected a flushing issue, but looking at the source code the
buffer_ostream should flush when going out-of-scope, and the raw_string_ostream
flushes in its str() getter. Adding additional flush() calls did not change the
output.
I'm using LLVM 3.5 vanilla and 3.7 from the Arch repositories, on Linux 64bit.</pre>
</div>
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