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| <h5 class="subsubsection">15.4.7.7 Known Peculiarities of Ada Mode</h5> |
| |
| <p><a name="index-Ada_002c-problems-878"></a> |
| Besides the omissions listed previously (see <a href="Omissions-from-Ada.html#Omissions-from-Ada">Omissions from Ada</a>), |
| we know of several problems with and limitations of Ada mode in |
| <span class="sc">gdb</span>, |
| some of which will be fixed with planned future releases of the debugger |
| and the GNU Ada compiler. |
| |
| <ul> |
| <li>Currently, the debugger |
| has insufficient information to determine whether certain pointers represent |
| pointers to objects or the objects themselves. |
| Thus, the user may have to tack an extra <code>.all</code> after an expression |
| to get it printed properly. |
| |
| <li>Static constants that the compiler chooses not to materialize as objects in |
| storage are invisible to the debugger. |
| |
| <li>Named parameter associations in function argument lists are ignored (the |
| argument lists are treated as positional). |
| |
| <li>Many useful library packages are currently invisible to the debugger. |
| |
| <li>Fixed-point arithmetic, conversions, input, and output is carried out using |
| floating-point arithmetic, and may give results that only approximate those on |
| the host machine. |
| |
| <li>The GNAT compiler never generates the prefix <code>Standard</code> for any of |
| the standard symbols defined by the Ada language. <span class="sc">gdb</span> knows about |
| this: it will strip the prefix from names when you use it, and will never |
| look for a name you have so qualified among local symbols, nor match against |
| symbols in other packages or subprograms. If you have |
| defined entities anywhere in your program other than parameters and |
| local variables whose simple names match names in <code>Standard</code>, |
| GNAT's lack of qualification here can cause confusion. When this happens, |
| you can usually resolve the confusion |
| by qualifying the problematic names with package |
| <code>Standard</code> explicitly. |
| </ul> |
| |
| <p>Older versions of the compiler sometimes generate erroneous debugging |
| information, resulting in the debugger incorrectly printing the value |
| of affected entities. In some cases, the debugger is able to work |
| around an issue automatically. In other cases, the debugger is able |
| to work around the issue, but the work-around has to be specifically |
| enabled. |
| |
| <p><a name="index-set-ada-trust_002dPAD_002dover_002dXVS-879"></a><a name="index-show-ada-trust_002dPAD_002dover_002dXVS-880"></a> |
| <dl> |
| <dt><code>set ada trust-PAD-over-XVS on</code><dd>Configure GDB to strictly follow the GNAT encoding when computing the |
| value of Ada entities, particularly when <code>PAD</code> and <code>PAD___XVS</code> |
| types are involved (see <code>ada/exp_dbug.ads</code> in the GCC sources for |
| a complete description of the encoding used by the GNAT compiler). |
| This is the default. |
| |
| <br><dt><code>set ada trust-PAD-over-XVS off</code><dd>This is related to the encoding using by the GNAT compiler. If <span class="sc">gdb</span> |
| sometimes prints the wrong value for certain entities, changing <code>ada |
| trust-PAD-over-XVS</code> to <code>off</code> activates a work-around which may fix |
| the issue. It is always safe to set <code>ada trust-PAD-over-XVS</code> to |
| <code>off</code>, but this incurs a slight performance penalty, so it is |
| recommended to leave this setting to <code>on</code> unless necessary. |
| |
| </dl> |
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