bsla_nonnullarg.h

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/// @file bsla_nonnullarg.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bsla_nonnullarg.h                                                  -*-C++-*-
#ifndef INCLUDED_BSLA_NONNULLARG
#define INCLUDED_BSLA_NONNULLARG
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bsla_nonnullarg bsla_nonnullarg
/// @brief  Provide macros to hint at null arguments to functions.
/// @addtogroup bsl
/// @{
/// @addtogroup bsla
/// @{
/// @addtogroup bsla_nonnullarg
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bsla_nonnullarg-purpose"> Purpose</a>
/// * <a href="#bsla_nonnullarg-macros"> Macros </a>
/// * <a href="#bsla_nonnullarg-description"> Description </a>
///   * <a href="#bsla_nonnullarg-macro-reference"> Macro Reference </a>
///   * <a href="#bsla_nonnullarg-usage"> Usage </a>
///     * <a href="#bsla_nonnullarg-example-1-passing-null-to-arguments-annotated-as-non-null"> Example 1: Passing Null to Arguments Annotated as Non-Null </a>
///
/// # Purpose {#bsla_nonnullarg-purpose}
/// Provide macros to hint at null arguments to functions.
///
/// # Macros {#bsla_nonnullarg-macros}
///
/// -  BSLA_NONNULLARGS: warn if any pointer arguments are null
/// -  BSLA_NONNULLARG(...): warn if indexed arguments are null
/// -  BSLA_NONNULLARGS_IS_ACTIVE: defined if `BSLA_NONNULLARGS` is active
/// -  BSLA_NONNULLARG_IS_ACTIVE:  defined if `BSLA_NONNULLARG`  is active
///
/// @see  bsla_annotations
///
/// # Description {#bsla_nonnullarg-description}
/// This component provides preprocessor macros that define
/// compiler-specific compile-time annotations.  These macros instruct the
/// compiler to warn if null is passed to certain arguments to a function, or,
/// on platforms where the feature is not supported, expand to nothing.
///
/// Note that the annotations cause warnings to be emitted if the covered
/// argument is passed:
/// * `NULL`
/// * 0
/// * `static_cast<TYPE *>(0)`
/// * `nullptr` (with C++11)
/// * a `const` variable known to be 0 (clang only, no warning with g++)
///
/// ## Macro Reference {#bsla_nonnullarg-macro-reference}
///
///
///  `BSLA_NONNULLARGS`:
///      This annotation indicates that a compiler warning is to be issued if
///      any of the pointer arguments to this function are passed null.
/// 
///  `BSLA_NONNULLARG(...)`:
///      This annotation, passed a variable-length list of positive integers,
///      indicates that a compiler warning is to be issued if null is passed to
///      a pointer argument at any of the specified indices, where the first
///      argument of the annotated function has an index of 1. Note that for
///      non-static member functions, the implicit `this` argument has index 1.
/// 
///  `BSLA_NONNULLARG_IS_ACTIVE`:
///      The macro `BSLA_NONNULLARGS_IS_ACTIVE` is defined if `BSLA_NONNULLARGS`
///      expands to something with the desired effect; otherwise
///      `BSLA_NONNULLARGS_IS_ACTIVE` is not defined and `BSLA_NONNULLARGS`
///      expands to nothing.
/// 
///  `BSLS_NONNULLARGS_IS_ACTIVE`:
///      The macro `BSLA_NONNULLARG_IS_ACTIVE` is defined if `BSLA_NONNULLARG`
///      expands to something with the desired effect; otherwise
///      `BSLA_NONNULLARG_IS_ACTIVE` is not defined and `BSLA_NONNULLARG`
///      expands to nothing.
///
/// ## Usage {#bsla_nonnullarg-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Passing Null to Arguments Annotated as Non-Null {#bsla_nonnullarg-example-1-passing-null-to-arguments-annotated-as-non-null}
///
///
/// First, we define a function, `usagePrint1`, annotated such that a compiler
/// warning will occur if the first argument of the annotated function is passed
/// 0, `NULL`, `nullptr`, or (on clang) a null pointer constant expression:
/// @code
/// // Print the specified 'string' the specified 'repetition' times.
/// void usagePrint1(const char *string, int repetition) BSLA_NONNULLARG(1);
///
/// void usagePrint1(const char *string, int repetition)
/// {
///     for (int ii = 0; ii < repetition; ++ii) {
///         printf("%s\n", string);
///     }
/// }
/// @endcode
/// Then, we define a nearly identical function annotated with
/// `BSLA_NONNULLARGS` instead.  Note that only pointer arguments are affected
/// by this annotation -- `repetition` is not affected and may be passed 0
/// without a warning being emitted:
/// @code
/// // Print the specified 'string' the specified 'repetition' times.
/// void usagePrint2(const char *string, int repetition) BSLA_NONNULLARGS;
///
/// void usagePrint2(const char *string, int repetition)
/// {
///     for (int ii = 0; ii < repetition; ++ii) {
///         printf("%s\n", string);
///     }
/// }
/// @endcode
/// So the two different annotations on these functions have an identical
/// effect -- affecting the `string` argument but not the `repetition` argument.
///
/// Next, in `main`, we call both functions with a non-null first argument, and
/// observe that no warning occurs.  Note that even though 0 is passed to the
/// integer argument to `usagePrint2` and the `BSLA_NONNULLARGS` annotation was
/// used, non-pointer arguments are not affected by that annotation:
/// @code
///     usagePrint1("woof", 0);
///     usagePrint2("meow", 0);
/// @endcode
/// Then, we call both functions passing the first argument a variable whose
/// value is known by the compiler to be null, but since `np1` is a non-`const`
/// variable, no warning is issued:
/// @code
///     char *np1 = NULL;
///     usagePrint1(np1,    0);
///     usagePrint2(np1,    0);
/// @endcode
/// Now, we call both functions passing various forms of constant null pointer
/// expressions to the first argument:
/// @code
///     usagePrint1(   0, -10);
///     usagePrint2(   0, -10);
///
///     usagePrint1(NULL, -20);
///     usagePrint2(NULL, -20);
///
///     usagePrint1(static_cast<char *>(0), -30);
///     usagePrint2(static_cast<char *>(0), -30);
///
///     #if __cplusplus >= 201103L
///         usagePrint1(nullptr, -40);
///         usagePrint2(nullptr, -40);
///     #endif
///
///     char * const np2 = 0;   // 'np2', unlike 'np1' above, is 'const'.
///     usagePrint1(np2, -50);    // Warning with clang, not g++
///     usagePrint2(np2, -50);    // Warning with clang, not g++
/// @endcode
/// Finally, we observe that the above calls result in the following warnings
/// with clang w/C++11 support:
/// @code
/// .../bsla_nonnullarg.t.cpp:376:30: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint1(   0, -10);
///                    ~     ^
/// .../bsla_nonnullarg.t.cpp:377:30: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint2(   0, -10);
///                    ~     ^
/// .../bsla_nonnullarg.t.cpp:379:30: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint1(NULL, -20);
///                 ~~~~     ^
/// .../bsla_nonnullarg.t.cpp:380:30: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint2(NULL, -20);
///                 ~~~~     ^
/// .../bsla_nonnullarg.t.cpp:382:48: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint1(static_cast<char *>(0), -30);
///                 ~~~~~~~~~~~~~~~~~~~~~~     ^
/// .../bsla_nonnullarg.t.cpp:383:48: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint2(static_cast<char *>(0), -30);
///                 ~~~~~~~~~~~~~~~~~~~~~~     ^
/// .../bsla_nonnullarg.t.cpp:386:37: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///         usagePrint1(nullptr, -40);
///                     ~~~~~~~     ^
/// .../bsla_nonnullarg.t.cpp:387:37: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///         usagePrint2(nullptr, -40);
///                     ~~~~~~~     ^
/// .../bsla_nonnullarg.t.cpp:391:29: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint1(np2, -50);    // Warning with clang, not g++
///                 ~~~     ^
/// .../bsla_nonnullarg.t.cpp:392:29: warning: null passed to a callee that
/// requires a non-null argument [-Wnonnull]
///     usagePrint2(np2, -50);    // Warning with clang, not g++
///                 ~~~     ^
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bsla
 * @{
 */
/** @addtogroup bsla_nonnullarg
 * @{
 */
 
#include <bsls_platform.h>
 
                       // =============================
                       // Checks for Pre-Defined macros
                       // =============================
 
#if defined(BSLA_NONNULLARG)
#error BSLA_NONNULLARG is already defined!
#endif
 
#if defined(BSLA_NONNULLARG_IS_ACTIVE)
#error BSLA_NONNULLARG_IS_ACTIVE is already defined!
#endif
 
#if defined(BSLA_NONNULLARGS)
#error BSLA_NONNULLARGS is already defined!
#endif
 
#if defined(BSLA_NONNULLARGS_IS_ACTIVE)
#error BSLA_NONNULLARGS_IS_ACTIVE is already defined!
#endif
                       // =========================
                       // Set macros as appropriate
                       // =========================
 
#if defined(BSLS_PLATFORM_CMP_GNU) || defined(BSLS_PLATFORM_CMP_CLANG)
    #define BSLA_NONNULLARG(...)   __attribute__((__nonnull__(__VA_ARGS__)))
    #define BSLA_NONNULLARGS       __attribute__((__nonnull__))
 
    #define BSLA_NONNULLARG_IS_ACTIVE  1
    #define BSLA_NONNULLARGS_IS_ACTIVE 1
#else
    #define BSLA_NONNULLARG(...)
    #define BSLA_NONNULLARGS
#endif
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2019 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */