[apparmor] [patch 19/24] Move buffer management for the interface to C++ ostringstream class

[Steve Beattie]

On Fri, Mar 07, 2014 at 09:31:40AM -0800, john.johansen at canonical.com wrote:
> Signed-off-by: John Johansen <john.johansen at canonical.com>
> ---
>  parser/parser.h           |    5 
>  parser/parser_interface.c |  510 +++++++++++++---------------------------------
>  parser/parser_policy.c    |    8 
>  3 files changed, 151 insertions(+), 372 deletions(-)

When compiling on 32 bit platforms after applying this patch, the
compiler vomits up the following warnings:

  g++ -g -O2 -pipe -Wall -Wsign-compare -Wmissing-field-initializers -Wformat-security -Wunused-parameter -std=gnu++0x -D_GNU_SOURCE  -DPACKAGE=\"apparmor-parser\" -DLOCALEDIR=\"/usr/share/locale\" -DSUBDOMAIN_CONFDIR=\"/etc/apparmor\" -I../libraries/libapparmor//include -c -o parser_interface.o parser_interface.c
  parser_interface.c: In function ‘void sd_write_aligned_blob(std::ostringstream&, void*, int, const char*)’:
  parser_interface.c:275:37: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: [enabled by default]
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                       ^
  parser_interface.c:269:23: note: in definition of macro ‘align64’
   #define align64(X) (((X) + (typeof(X)) 7) & ~((typeof(X)) 7))
                         ^
  In file included from /usr/include/c++/4.8/bits/char_traits.h:40:0,
                   from /usr/include/c++/4.8/string:40,
                   from parser_interface.c:30:
  /usr/include/c++/4.8/bits/postypes.h:178:7: note: candidate 1: std::fpos<_StateT> std::fpos<_StateT>::operator+(std::streamoff) const [with _StateT = __mbstate_t; std::streamoff = long long int]
         operator+(streamoff __off) const
         ^
  parser_interface.c:275:37: note: candidate 2: operator+(std::streamoff {aka long long int}, long int) <built-in>
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                       ^
  parser_interface.c:269:23: note: in definition of macro ‘align64’
   #define align64(X) (((X) + (typeof(X)) 7) & ~((typeof(X)) 7))
                         ^
  parser_interface.c:275:37: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: [enabled by default]
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                       ^
  parser_interface.c:269:36: note: in definition of macro ‘align64’
   #define align64(X) (((X) + (typeof(X)) 7) & ~((typeof(X)) 7))
                                      ^
  In file included from /usr/include/c++/4.8/bits/char_traits.h:40:0,
                   from /usr/include/c++/4.8/string:40,
                   from parser_interface.c:30:
  /usr/include/c++/4.8/bits/postypes.h:178:7: note: candidate 1: std::fpos<_StateT> std::fpos<_StateT>::operator+(std::streamoff) const [with _StateT = __mbstate_t; std::streamoff = long long int]
         operator+(streamoff __off) const
         ^
  parser_interface.c:275:37: note: candidate 2: operator+(std::streamoff {aka long long int}, long int) <built-in>
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                       ^
  parser_interface.c:269:36: note: in definition of macro ‘align64’
   #define align64(X) (((X) + (typeof(X)) 7) & ~((typeof(X)) 7))
                                      ^
  parser_interface.c:275:37: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: [enabled by default]
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                       ^
  parser_interface.c:269:55: note: in definition of macro ‘align64’
   #define align64(X) (((X) + (typeof(X)) 7) & ~((typeof(X)) 7))
                                                         ^
  In file included from /usr/include/c++/4.8/bits/char_traits.h:40:0,
                   from /usr/include/c++/4.8/string:40,
                   from parser_interface.c:30:
  /usr/include/c++/4.8/bits/postypes.h:178:7: note: candidate 1: std::fpos<_StateT> std::fpos<_StateT>::operator+(std::streamoff) const [with _StateT = __mbstate_t; std::streamoff = long long int]
         operator+(streamoff __off) const
         ^
  parser_interface.c:275:37: note: candidate 2: operator+(std::streamoff {aka long long int}, long int) <built-in>
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                       ^
  parser_interface.c:269:55: note: in definition of macro ‘align64’
   #define align64(X) (((X) + (typeof(X)) 7) & ~((typeof(X)) 7))
                                                         ^
  parser_interface.c:275:58: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: [enabled by default]
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                                            ^
  In file included from /usr/include/c++/4.8/bits/char_traits.h:40:0,
                   from /usr/include/c++/4.8/string:40,
                   from parser_interface.c:30:
  /usr/include/c++/4.8/bits/postypes.h:178:7: note: candidate 1: std::fpos<_StateT> std::fpos<_StateT>::operator+(std::streamoff) const [with _StateT = __mbstate_t; std::streamoff = long long int]
         operator+(streamoff __off) const
         ^
  parser_interface.c:275:58: note: candidate 2: operator+(std::streamoff {aka long long int}, long int) <built-in>
    size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
                                                            ^

I freely admit that I don't quite get what's going wrong here, except
that there's some ambiguity between the type returned by
std::ostringstream.tellp() (which is std::streamoff) and 5l. The
following silences the warnings (and doesn't produce them on 64 bit
platforms), but I'm not confident it's the right solution.

---
 parser/parser_interface.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: b/parser/parser_interface.c
===================================================================
--- a/parser/parser_interface.c
+++ b/parser/parser_interface.c
@@ -269,7 +269,7 @@ inline void sd_write_aligned_blob(std::o
 {
 	sd_write_name(buf, name);
 	/* pad calculation MUST come after name is written */
-	size_t pad = align64(buf.tellp() + 5l) - (buf.tellp() + 5l);
+	size_t pad = align64(buf.tellp() + ((std::streamoff) 5l)) - (buf.tellp() + ((std::streamoff) 5l));
 	sd_write8(buf, SD_BLOB);
 	sd_write32(buf, b_size + pad);
 	buf.write(zeros, pad);


-- 
Steve Beattie
<sbeattie at ubuntu.com>
http://NxNW.org/~steve/
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