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Doc: Delete obsolete interface.texi chapter from GCC internals manual

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The "Interfacing to GCC Output" chapter used to be part of the
user-facing GCC documentation but ended up in the GCC internals manual
when the two documents were separated in 2001.  It hasn't been updated
in any substantive way since then, and is now very bit-rotten.  (PCC is
no longer the "standard compiler" on any target, and the target-specific
issues mentioned are for very old architectures.)

Meanwhile, the GCC user documentation now has a chapter called "Binary
Compatibility" that covers ABI issues in a generic way and also covers
C++ compatibility.  Let's keep that one and throw out the obsolete
text that seems to predate the whole notion of an ABI.

gcc/ChangeLog
	* Makefile.in (TEXI_GCCINT_FILES): Remove interface.texi.
	* doc/gccint.texi (Top): Remove menu entry for the "interface" node,
	and include of interface.texi.
	* doc/interface.texi: Delete.
This commit is contained in:
Sandra Loosemore 2025-02-12 00:17:30 +00:00
parent 2605daa6b8
commit 29a5b1bdd9
3 changed files with 2 additions and 75 deletions
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2
gcc/Makefile.in
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@ -3697,7 +3697,7 @@ TEXI_GCC_FILES = gcc.texi gcc-common.texi gcc-vers.texi frontends.texi \
# the *.texi files have changed.
TEXI_GCCINT_FILES = gccint.texi gcc-common.texi gcc-vers.texi \
contribute.texi makefile.texi configterms.texi options.texi \
portability.texi interface.texi passes.texi rtl.texi md.texi \
portability.texi passes.texi rtl.texi md.texi \
$(srcdir)/doc/tm.texi hostconfig.texi fragments.texi \
configfiles.texi collect2.texi headerdirs.texi funding.texi \
gnu.texi gpl_v3.texi fdl.texi contrib.texi languages.texi \

5
gcc/doc/gccint.texi
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@ -87,8 +87,7 @@ Compiler Collection (GCC)}.
This manual is mainly a reference manual rather than a tutorial. It
discusses how to contribute to GCC (@pxref{Contributing}), the
characteristics of the machines supported by GCC as hosts and targets
(@pxref{Portability}), how GCC relates to the ABIs on such systems
(@pxref{Interface}), and the characteristics of the languages for
(@pxref{Portability}), and the characteristics of the languages for
which GCC front ends are written (@pxref{Languages}). It then
describes the GCC source tree structure and build system, some of the
interfaces to GCC front ends, and how support for a target system is
@ -100,7 +99,6 @@ Additional tutorial information is linked to from
@menu
* Contributing:: How to contribute to testing and developing GCC.
* Portability:: Goals of GCC's portability features.
* Interface:: Function-call interface of GCC output.
* Libgcc:: Low-level runtime library used by GCC.
* Languages:: Languages for which GCC front ends are written.
* Source Tree:: GCC source tree structure and build system.
@ -141,7 +139,6 @@ Additional tutorial information is linked to from
@include contribute.texi
@include portability.texi
@include interface.texi
@include libgcc.texi
@include languages.texi
@include sourcebuild.texi

70
gcc/doc/interface.texi
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@ -1,70 +0,0 @@
@c Copyright (C) 1988-2025 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@node Interface
@chapter Interfacing to GCC Output
@cindex interfacing to GCC output
@cindex run-time conventions
@cindex function call conventions
@cindex conventions, run-time
GCC is normally configured to use the same function calling convention
normally in use on the target system. This is done with the
machine-description macros described (@pxref{Target Macros}).
@cindex unions, returning
@cindex structures, returning
@cindex returning structures and unions
However, returning of structure and union values is done differently on
some target machines. As a result, functions compiled with PCC
returning such types cannot be called from code compiled with GCC,
and vice versa. This does not cause trouble often because few Unix
library routines return structures or unions.
GCC code returns structures and unions that are 1, 2, 4 or 8 bytes
long in the same registers used for @code{int} or @code{double} return
values. (GCC typically allocates variables of such types in
registers also.) Structures and unions of other sizes are returned by
storing them into an address passed by the caller (usually in a
register). The target hook @code{TARGET_STRUCT_VALUE_RTX}
tells GCC where to pass this address.
By contrast, PCC on most target machines returns structures and unions
of any size by copying the data into an area of static storage, and then
returning the address of that storage as if it were a pointer value.
The caller must copy the data from that memory area to the place where
the value is wanted. This is slower than the method used by GCC, and
fails to be reentrant.
On some target machines, such as RISC machines and the 80386, the
standard system convention is to pass to the subroutine the address of
where to return the value. On these machines, GCC has been
configured to be compatible with the standard compiler, when this method
is used. It may not be compatible for structures of 1, 2, 4 or 8 bytes.
@cindex argument passing
@cindex passing arguments
GCC uses the system's standard convention for passing arguments. On
some machines, the first few arguments are passed in registers; in
others, all are passed on the stack. It would be possible to use
registers for argument passing on any machine, and this would probably
result in a significant speedup. But the result would be complete
incompatibility with code that follows the standard convention. So this
change is practical only if you are switching to GCC as the sole C
compiler for the system. We may implement register argument passing on
certain machines once we have a complete GNU system so that we can
compile the libraries with GCC@.
On some machines (particularly the SPARC), certain types of arguments
are passed ``by invisible reference''. This means that the value is
stored in memory, and the address of the memory location is passed to
the subroutine.
@cindex @code{longjmp} and automatic variables
If you use @code{longjmp}, beware of automatic variables. ISO C says that
automatic variables that are not declared @code{volatile} have undefined
values after a @code{longjmp}. And this is all GCC promises to do,
because it is very difficult to restore register variables correctly, and
one of GCC's features is that it can put variables in registers without
your asking it to.