balst_objectfileformat.h

Go to the documentation of this file.

/// @file balst_objectfileformat.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// balst_objectfileformat.h                                           -*-C++-*-
#ifndef INCLUDED_BALST_OBJECTFILEFORMAT
#define INCLUDED_BALST_OBJECTFILEFORMAT
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup balst_objectfileformat balst_objectfileformat
/// @brief  Provide platform-dependent object file format trait definitions.
/// @addtogroup bal
/// @{
/// @addtogroup balst
/// @{
/// @addtogroup balst_objectfileformat
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#balst_objectfileformat-purpose"> Purpose</a>
/// * <a href="#balst_objectfileformat-classes"> Classes </a>
/// * <a href="#balst_objectfileformat-description"> Description </a>
///   * <a href="#balst_objectfileformat-dwarf-information"> DWARF Information </a>
///     * <a href="#balst_objectfileformat-implementation-note"> Implementation Note </a>
///   * <a href="#balst_objectfileformat-usage"> Usage </a>
///     * <a href="#balst_objectfileformat-example-1-accessing-balst-objectfileformat-information-at-run-time"> Example 1: Accessing balst::ObjectFileFormat Information at Run Time </a>
///
/// # Purpose {#balst_objectfileformat-purpose}
/// Provide platform-dependent object file format trait definitions.
///
/// # Classes {#balst_objectfileformat-classes}
///
/// -   balst::ObjectFileFormat: namespace for object file format traits
///
/// @see 
///
/// # Description {#balst_objectfileformat-description}
/// This component defines a set of traits that identify and
/// describe a platform's object file format properties.  For example, the
/// `balst::ObjectFileFormat::ResolverPolicy` trait is ascribed a "value" (i.e.,
/// `Elf` or `Xcoff`) appropriate for each supported platform.  The various
/// stack trace traits are actually types declared in the
/// `bdescu_ObjectFileFormat` `struct`.  These types are intended to be used in
/// specializing template implementations or to enable function overloading
/// based on the prevalent system's characteristics.  #defines are also
/// provided by this component to facilitate conditional compilation depending
/// upon object file formats.
///
/// ## DWARF Information {#balst_objectfileformat-dwarf-information}
///
///
/// DWARF is a format for detailed debugging information.  It is not a complete
/// format, but is used within other formats.  It is used within ELF on Linux,
/// but not (yet) on Solaris at Bloomberg (currently the ELF format on Solaris
/// still uses STABS).  It is used within the Mach-O format (also known as the
/// `Dladdr` format in this file) used on Darwin.  It is also used by the Clang
/// compiler (which uses ELF).
///
/// For all these platforms, parsing the DWARF information is necessary for the
/// stack trace to get source file names and line numbers (the ELF format gives
/// source file names, but only in the case of file-scope static functions).
///
/// DWARF is implemented for g++ versions earlier than 7.1.0 on Linux.
///
/// ### Implementation Note {#balst_objectfileformat-implementation-note}
///
///
/// Linux g++ 7.1.0 uses DWARF version 4, while g++ 5.4.0 and before use DWARF
/// version 3.  At the moment the required system header, `dwarf.h`, is not
/// available in the Bloomberg production build `chroot` environment, so
/// support for dwarf formats is disabled.
///
/// DWARF support on Clang is problematic and not currrently implemented, see
/// the long comment in balst_resolverimpl_elf.cpp, which explains exactly how
/// it could be implemented when that becomes a priority.
///
/// We have not yet investigated implementing DWARF for Dladdr (Darwin).
///
/// ## Usage {#balst_objectfileformat-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Accessing balst::ObjectFileFormat Information at Run Time {#balst_objectfileformat-example-1-accessing-balst-objectfileformat-information-at-run-time}
///
///
/// The templated (specialized) `typeTest` function returns a unique, non-zero
/// value when passed an object of types
/// `balst::ObjectFileFormat::{Elf,Xcoff,Windows}`, and 0 otherwise.
/// @code
/// template <typename TYPE>
/// int typeTest(const TYPE &)
/// {
///     return 0;
/// }
///
/// int typeTest(const balst::ObjectFileFormat::Elf &)
/// {
///     return 1;
/// }
///
/// int typeTest(const balst::ObjectFileFormat::Xcoff &)
/// {
///     return 2;
/// }
///
/// int typeTest(const balst::ObjectFileFormat::Windows &)
/// {
///     return 3;
/// }
///
/// int main() ...
/// @endcode
/// We define an object `policy` of type `balst::ObjectFileFormat::Policy`,
/// which will be of type `...::Elf`, `...::Xcoff`, or `...::Windows`
/// appropriate for the platform.
/// @code
///     balst::ObjectFileFormat::Policy policy;
/// @endcode
/// We now test it using `typeTest`:
/// @code
///     assert(typeTest(policy) > 0);
///
/// #if defined(BALST_OBJECTFILEFORMAT_RESOLVER_ELF)
///     assert(1 == typeTest(policy));
/// #endif
///
/// #if defined(BALST_OBJECTFILEFORMAT_RESOLVER_XCOFF)
///     assert(2 == typeTest(policy));
/// #endif
///
/// #if defined(BALST_OBJECTFILEFORMAT_RESOLVER_WINDOWS)
///     assert(3 == typeTest(policy));
/// #endif
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bal
 * @{
 */
/** @addtogroup balst
 * @{
 */
/** @addtogroup balst_objectfileformat
 * @{
 */
 
#include <balscm_version.h>
 
#include <bsls_platform.h>
 
 
 
namespace balst {
                           // ======================
                           // class ObjectFileFormat
                           // ======================
 
/// This `struct` is named `ObjectFileFormat` for historical reasons, what
/// it really determines is resolving strategy.  Linux, for example, can be
/// resolved using either the `Elf` or `Dladdr` policies.  We choose `Elf`
/// for linux because that mode of resolving yields more information.
struct ObjectFileFormat {
 
    struct Elf {};        // resolve as elf object
 
    struct Xcoff {};      // resolve as xcoff object
 
    struct Windows {};    // format used on Microsoft Windows platform
 
    struct Dladdr {};     // resolve using the 'dladdr' call
 
    struct Dummy {};
 
#if defined(BSLS_PLATFORM_OS_SOLARIS) || \
    defined(BSLS_PLATFORM_OS_LINUX)
 
    typedef Elf Policy;
#   define BALST_OBJECTFILEFORMAT_RESOLVER_ELF 1
 
# if defined(BSLS_PLATFORM_OS_LINUX) && defined(BSLS_PLATFORM_CMP_GNU)
#   define BALST_OBJECTFILEFORMAT_RESOLVER_DWARF 1
# endif
 
#elif defined(BSLS_PLATFORM_OS_AIX)
 
    typedef Xcoff Policy;
#   define BALST_OBJECTFILEFORMAT_RESOLVER_XCOFF 1
 
#elif defined(BSLS_PLATFORM_OS_WINDOWS)
 
    typedef Windows Policy;
#   define BALST_OBJECTFILEFORMAT_RESOLVER_WINDOWS 1
 
#elif defined(BSLS_PLATFORM_OS_DARWIN)
 
    typedef Dladdr Policy;
#   define BALST_OBJECTFILEFORMAT_RESOLVER_DLADDR 1
 
#else
 
    typedef Dummy Policy;
#   error unrecognized platform
#   define BALST_OBJECTFILEFORMAT_RESOLVER_UNIMPLEMENTED 1
 
#endif
 
};
}  // close package namespace
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2015 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */