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clarify -fno-globals docs 

From-SVN: r25277
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Craig Burley 1999-02-18 03:02:04 +00:00 committed by Craig Burley
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2 changed files with 58 additions and 24 deletions
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4
gcc/f/ChangeLog
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@ -1,3 +1,7 @@
1999-02-18 Craig Burley <craig@jcb-sc.com>
* g77.texi: Clarify -fno-globals vs. -Wno-globals.
1999-02-18 Craig Burley <craig@jcb-sc.com>
* intdoc.in (LOG10): Fix typo.

78
gcc/f/g77.texi
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@ -3282,6 +3282,8 @@ arguments.
@item -fno-globals
@cindex global names, warning
@cindex warnings, global names
@cindex in-line code
@cindex compilation, in-line
Disable diagnostics about inter-procedural
analysis problems, such as disagreements about the
type of a function or a procedure's argument,
@ -3298,9 +3300,8 @@ code that would otherwise be diagnosed.
As such, this option might be quite useful when
compiling existing, ``working'' code that happens
to have a few bugs that do not generally show
themselves, but @code{g77} exposes via a
diagnostic.
to have a few bugs that do not generally show themselves,
but which @code{g77} diagnoses.
Use of this option therefore has the effect of
instructing @code{g77} to behave more like it did
@ -3314,7 +3315,11 @@ Without this option, @code{g77} defaults to performing
the potentially inlining procedures as it started doing
in version 0.5.20, but as of version 0.5.21, it also
diagnoses disagreements that might cause such inlining
to crash the compiler.
to crash the compiler as (fatal) errors,
and warns about similar disagreements
that are currently believed to not
likely to result in the compiler later crashing
or producing incorrect code.
@end table
@xref{Code Gen Options,,Options for Code Generation Conventions,
@ -15208,29 +15213,54 @@ Argument #@var{n} of @var{name} is @dots{}
@end smallexample
These messages all identify disagreements about the
global procedure named @var{name} among different program
units (usually including @var{name} itself).
global procedure named @var{name} among different program units
(usually including @var{name} itself).
These disagreements, if not diagnosed, could result in a
compiler crash if the compiler attempted to inline a reference
to @var{name} within a calling program unit that disagreed
with the @var{name} program unit regarding whether the
procedure is a subroutine or function, the type of the
return value of the procedure (if it is a function), the
number of arguments the procedure accepts, or the type
of each argument.
Whether a particular disagreement is reported
as a warning or an error
can depend on the relative order
of the disagreeing portions of the source file.
Such disagreements @emph{should} be fixed in the Fortran
code itself.
However, if that is not immediately practical, and the code
has been working for some time, it is possible it will work
when compiled by @code{g77} with the @samp{-fno-globals} option.
Disagreements between a procedure invocation
and the @emph{subsequent} procedure itself
are, usually, diagnosed as errors
when the procedure itself @emph{precedes} the invocation.
Other disagreements are diagnosed via warnings.
The @samp{-fno-globals} option disables these diagnostics, and
also disables all inlining of references to global procedures
to avoid compiler crashes.
The diagnostics are actually produced, but as warnings, unless
the @samp{-Wno-globals} option also is specified.
@cindex forward references
@cindex in-line code
@cindex compilation, in-line
This distinction, between warnings and errors,
is due primarily to the present tendency of the @code{gcc} back end
to inline only those procedure invocations that are
@emph{preceded} by the corresponding procedure definitions.
If the @code{gcc} back end is changed
to inline ``forward references'',
in which invocations precede definitions,
the @code{g77} front end will be changed
to treat both orderings as errors, accordingly.
The sorts of disagreements that are diagnosed by @code{g77} include
whether a procedure is a subroutine or function;
if it is a function, the type of the return value of the procedure;
the number of arguments the procedure accepts;
and the type of each argument.
Disagreements regarding global names among program units
in a Fortran program @emph{should} be fixed in the code itself.
However, if that is not immediately practical,
and the code has been working for some time,
it is possible it will work
when compiled with the @samp{-fno-globals} option.
The @samp{-fno-globals} option
causes these diagnostics to all be warnings
and disables all inlining of references to global procedures
(to avoid subsequent compiler crashes and bad-code generation).
Use of the @samp{-Wno-globals} option as well as @samp{-fno-globals}
suppresses all of these diagnostics.
(@samp{-Wno-globals} by itself disables only the warnings,
not the errors.)
After using @samp{-fno-globals} to work around these problems,
it is wise to stop using that option and address them by fixing