8.1.14.2 Symbolic Traceback

A symbolic traceback is a stack traceback in which procedure names are associated with each code location.

Note that this feature is not supported on all platforms. See GNAT.Traceback.Symbolic spec in g-trasym.ads for a complete list of currently supported platforms.

Note that the symbolic traceback requires that the program be compiled with debug information. If it is not compiled with debug information only the non-symbolic information will be valid.

Tracebacks From Exception Occurrences

Here is an example:

    with Ada.Text_IO;
    with GNAT.Traceback.Symbolic;
    
    procedure STB is
    
       procedure P1 is
       begin
          raise Constraint_Error;
       end P1;
    
       procedure P2 is
       begin
          P1;
       end P2;
    
       procedure P3 is
       begin
          P2;
       end P3;
    
    begin
       P3;
    exception
       when E : others =>
          Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
    end STB;

    $ gnatmake -g .\stb -bargs -E
    $ stb
    
    0040149F in stb.p1 at stb.adb:8
    004014B7 in stb.p2 at stb.adb:13
    004014CF in stb.p3 at stb.adb:18
    004015DD in ada.stb at stb.adb:22
    00401461 in main at b~stb.adb:168
    004011C4 in __mingw_CRTStartup at crt1.c:200
    004011F1 in mainCRTStartup at crt1.c:222
    77E892A4 in ?? at ??:0

In the above example the .\ syntax in the `gnatmake' command is currently required by `addr2line' for files that are in the current working directory. Moreover, the exact sequence of linker options may vary from platform to platform. The above `-largs' section is for Windows platforms. By contrast, under Unix there is no need for the `-largs' section. Differences across platforms are due to details of linker implementation.

Tracebacks From Anywhere in a Program

It is possible to get a symbolic stack traceback from anywhere in a program, just as for non-symbolic tracebacks. The first step is to obtain a non-symbolic traceback, and then call Symbolic_Traceback to compute the symbolic information. Here is an example:

    with Ada.Text_IO;
    with GNAT.Traceback;
    with GNAT.Traceback.Symbolic;
    
    procedure STB is
    
       use Ada;
       use GNAT.Traceback;
       use GNAT.Traceback.Symbolic;
    
       procedure P1 is
          TB  : Tracebacks_Array (1 .. 10);
          --  We are asking for a maximum of 10 stack frames.
          Len : Natural;
          --  Len will receive the actual number of stack frames returned.
       begin
          Call_Chain (TB, Len);
          Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
       end P1;
    
       procedure P2 is
       begin
          P1;
       end P2;
    
    begin
       P2;
    end STB;