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* stabs.texinfo (Local Variable Parameters): Re-write paragraph on

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floats passed as doubles (to improve clarity).
This commit is contained in:
Jim Kingdon 1993-10-20 23:13:46 +00:00
parent 921f2b29a9
commit 9ab86fa36e
2 changed files with 31 additions and 9 deletions
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7
gdb/doc/ChangeLog
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@ -1,6 +1,11 @@
Wed Oct 20 18:07:44 1993 Jim Kingdon (kingdon@lioth.cygnus.com)
* stabs.texinfo (Local Variable Parameters): Re-write paragraph on
floats passed as doubles (to improve clarity).
Tue Oct 19 14:21:18 1993 Roland H. Pesch (pesch@fowanton.cygnus.com)
* gdb.texinfo (Sourc Path): index entries for $cwd, $pdir
* gdb.texinfo (Source Path): index entries for $cwd, $pdir
* a4rc.sed: update to work with Andreas Vogel papersize params

33
gdb/doc/stabs.texinfo
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@ -1091,15 +1091,32 @@ happens when the argument was passed in a register and then the compiler
stores it as a local variable. If possible, the compiler should claim
that it's in a register, but this isn't always done.
@findex N_LSYM, for parameter
Some compilers use the pair of symbols approach described above
(@samp{@var{arg}:p} followed by @samp{@var{arg}:}); this includes GCC1
(not GCC2) on the sparc when passing a small structure and GCC2
(sometimes) when the argument type is @code{float} and it is passed as a
@code{double} and converted to @code{float} by the prologue (in the
latter case the type of the @samp{@var{arg}:p} symbol is @code{double}
and the type of the @samp{@var{arg}:} symbol is @code{float}).
If a parameter is passed as one type and converted to a smaller type by
the prologue (for example, the parameter is declared as a @code{float},
but the calling conventions specify that it is passed as a
@code{double}), then GCC2 (sometimes) uses a pair of symbols. The first
symbol uses symbol descriptor @samp{p} and the type which is passed.
The second symbol has the type and location which the parameter actually
has after the prologue. For example, suppose the following C code
appears with no prototypes involved:
@example
void
subr (f)
float f;
@{
@end example
if @code{f} gets allocated in a register, then its stabs look like:
@c FIXME: Probably should run this through the compiler and get the
@c whole thing including ".stabs" and so on.
@example
f:p13 # @r{where 13 is double}
f:r12 # @r{where 12 is float}
@end example
@findex N_LSYM, for parameter
GCC, at least on the 960, has another solution to the same problem. It
uses a single @samp{p} symbol descriptor for an argument which is stored
as a local variable but uses @code{N_LSYM} instead of @code{N_PSYM}. In