gcc/fortran/doc/gfortran/gnu-fortran-command-options/options-for-debugging-your-program-or-gnu-fortran.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. index:: options, debugging, debugging information options
   7
   8 .. _debugging-options:
   9
  10 Options for debugging your program or GNU Fortran
  11 *************************************************
  12
  13 GNU Fortran has various special options that are used for debugging
  14 either your program or the GNU Fortran compiler.
  15
  16 .. index:: fdump-fortran-original
  17
  18 .. option:: -fdump-fortran-original
  19
  20   Output the internal parse tree after translating the source program
  21   into internal representation.  This option is mostly useful for
  22   debugging the GNU Fortran compiler itself. The output generated by
  23   this option might change between releases. This option may also
  24   generate internal compiler errors for features which have only
  25   recently been added.
  26
  27 .. index:: fdump-fortran-optimized
  28
  29 .. option:: -fdump-fortran-optimized
  30
  31   Output the parse tree after front-end optimization.  Mostly useful for
  32   debugging the GNU Fortran compiler itself. The output generated by
  33   this option might change between releases.  This option may also
  34   generate internal compiler errors for features which have only
  35   recently been added.
  36
  37 .. index:: fdump-parse-tree
  38
  39 .. option:: -fdump-parse-tree
  40
  41   Output the internal parse tree after translating the source program
  42   into internal representation.  Mostly useful for debugging the GNU
  43   Fortran compiler itself. The output generated by this option might
  44   change between releases. This option may also generate internal
  45   compiler errors for features which have only recently been added. This
  46   option is deprecated; use ``-fdump-fortran-original`` instead.
  47
  48 .. index:: fdebug-aux-vars
  49
  50 .. option:: -fdebug-aux-vars
  51
  52   Renames internal variables created by the gfortran front end and makes
  53   them accessible to a debugger.  The name of the internal variables then
  54   start with upper-case letters followed by an underscore.  This option is
  55   useful for debugging the compiler's code generation together with
  56   ``-fdump-tree-original`` and enabling debugging of the executable
  57   program by using ``-g`` or ``-ggdb3``.
  58
  59 .. index:: fdump-fortran-global
  60
  61 .. option:: -fdump-fortran-global
  62
  63   Output a list of the global identifiers after translating into
  64   middle-end representation. Mostly useful for debugging the GNU Fortran
  65   compiler itself. The output generated by this option might change
  66   between releases.  This option may also generate internal compiler
  67   errors for features which have only recently been added.
  68
  69 .. index:: ffpe-trap=list
  70
  71 .. option:: -ffpe-trap={list}
  72
  73   Specify a list of floating point exception traps to enable.  On most
  74   systems, if a floating point exception occurs and the trap for that
  75   exception is enabled, a SIGFPE signal will be sent and the program
  76   being aborted, producing a core file useful for debugging.  :samp:`{list}`
  77   is a (possibly empty) comma-separated list of the following
  78   exceptions: :samp:`invalid` (invalid floating point operation, such as
  79   ``SQRT(-1.0)``), :samp:`zero` (division by zero), :samp:`overflow`
  80   (overflow in a floating point operation), :samp:`underflow` (underflow
  81   in a floating point operation), :samp:`inexact` (loss of precision
  82   during operation), and :samp:`denormal` (operation performed on a
  83   denormal value).  The first five exceptions correspond to the five
  84   IEEE 754 exceptions, whereas the last one (:samp:`denormal`) is not
  85   part of the IEEE 754 standard but is available on some common
  86   architectures such as x86.
  87
  88   The first three exceptions (:samp:`invalid`, :samp:`zero`, and
  89   :samp:`overflow`) often indicate serious errors, and unless the program
  90   has provisions for dealing with these exceptions, enabling traps for
  91   these three exceptions is probably a good idea.
  92
  93   If the option is used more than once in the command line, the lists will
  94   be joined: '  ``ffpe-trap=``:samp:`{list1}`  ``ffpe-trap=``:samp:`{list2}` '
  95   is equivalent to  ``ffpe-trap=``:samp:`{list1}`, :samp:`{list2}`.
  96
  97   Note that once enabled an exception cannot be disabled (no negative form).
  98
  99   Many, if not most, floating point operations incur loss of precision
 100   due to rounding, and hence the ``ffpe-trap=inexact`` is likely to
 101   be uninteresting in practice.
 102
 103   By default no exception traps are enabled.
 104
 105 .. index:: ffpe-summary=list
 106
 107 .. option:: -ffpe-summary={list}
 108
 109   Specify a list of floating-point exceptions, whose flag status is printed
 110   to ``ERROR_UNIT`` when invoking ``STOP`` and ``ERROR STOP``.
 111   :samp:`{list}` can be either :samp:`none`, :samp:`all` or a comma-separated list
 112   of the following exceptions: :samp:`invalid`, :samp:`zero`, :samp:`overflow`,
 113   :samp:`underflow`, :samp:`inexact` and :samp:`denormal`. (See
 114   :option:`-ffpe-trap` for a description of the exceptions.)
 115
 116   If the option is used more than once in the command line, only the
 117   last one will be used.
 118
 119   By default, a summary for all exceptions but :samp:`inexact` is shown.
 120
 121 .. index:: fno-backtrace, backtrace, trace
 122
 123 .. option:: -fno-backtrace
 124
 125   When a serious runtime error is encountered or a deadly signal is
 126   emitted (segmentation fault, illegal instruction, bus error,
 127   floating-point exception, and the other POSIX signals that have the
 128   action :samp:`core`), the Fortran runtime library tries to output a
 129   backtrace of the error. ``-fno-backtrace`` disables the backtrace
 130   generation. This option only has influence for compilation of the
 131   Fortran main program.
 132
 133 See :ref:`gcc:debugging-options`, for more information on
 134 debugging options.