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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Preprocessor too eager to stringify in assembler-with-cpp mode?"
href="http://llvm.org/bugs/show_bug.cgi?id=16371">16371</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Preprocessor too eager to stringify in assembler-with-cpp mode?
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</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>Frontend
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>aseipp@pobox.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>While continuing my porting GHC-to-clang work, I have run into a rather odd
discrepancy in the way Clang's preprocessor handles hashes in parameters and
whatnot vs GCC, and I'm not sure if this is a bug or not. :)
Here is a minimal test case vs GCC 4.7.3:
--------------------------------------------------------
$ gcc -E -undef -traditional -x assembler-with-cpp -o - -
#define foo(a,b,c) \
test asdfx# a b c
foo(a,b,c)
foo(a#,b#,c#)
^D
# 1 "<stdin>"
# 1 "<command-line>"
# 1 "<stdin>"
test asdfx# a b c
test asdfx# a# b# c#
$
$ clang -E -undef -traditional -x assembler-with-cpp -o - -
#define foo(a,b,c) \
test asdfx# a b c
foo(a,b,c)
foo(a#,b#,c#)
^D
# 1 "<stdin>"
# 1 "<built-in>" 1
# 1 "<stdin>" 2
test asdfx"a" b c
test asdfx"a#" b# c#
--------------------------------------------------------
Note the stringification of the first argument. I'm not sure if this
discrepancy is expected, but we force assembler-with-cpp mode in GHC now.
Perhaps this could be alleviated.
As a more extreme test case, consider the test from <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Segmentation fault when preprocessing in assembler-with-cpp mode"
href="show_bug.cgi?id=16363">bug 16363</a>, cut down
slightly (this is Haskell code but the deficiency should be obvious)
GCC:
--------------------------------------------------------
$ gcc -E -undef -traditional -x assembler-with-cpp -o - -
#define derivePrim(ty, ctr, sz, align) \
instance Prim ty where { \
sizeOf# _ = unI# sz \
; alignment# _ = unI# align
derivePrim(Word, W#, sIZEOF_WORD, aLIGNMENT_WORD)
# 1 "<stdin>"
# 1 "<command-line>"
# 1 "<stdin>"
instance Prim Word where { sizeOf# _ =
unI# sIZEOF_WORD ; alignment# _ =
unI# aLIGNMENT_WORD
--------------------------------------------------------
Clang:
--------------------------------------------------------
$ clang -E -undef -traditional -x assembler-with-cpp -o - -
#define derivePrim(ty, ctr, sz, align) \
instance Prim ty where { \
sizeOf# _ = unI# sz \
; alignment# _ = unI# align
derivePrim(Word, W#, sIZEOF_WORD, aLIGNMENT_WORD)
# 1 "<stdin>"
# 1 "<built-in>" 1
# 1 "<stdin>" 2
instance Prim Word where { sizeOf# _ = unI" sIZEOF_WORD" ; alignment# _ = unI"
aLIGNMENT_WORD"
--------------------------------------------------------
If it's not outrageous, could this be accommodated at all?
Attached is a file containing the problematic parts (it is a smaller version of
the attachment from <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Segmentation fault when preprocessing in assembler-with-cpp mode"
href="show_bug.cgi?id=16363">bug 16363</a>.) You can run 'gcc -E -x assembler-with-cpp' over
it to see the expected output vs what Clang outputs.</pre>
</div>
</p>
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