-@node The Compiler, The Debugger, Introduction, Top
+@node The Compiler
@comment node-name, next, previous, up
@chapter The Compiler
* Open Coding and Inline Expansion::
@end menu
-@node Error Messages, Handling of Types, The Compiler, The Compiler
+@node Error Messages
@comment node-name, next, previous, up
@section Error Messages
@cindex Error messages, Compiler
* Read Errors::
@end menu
-@node The Parts of the Error Message, The Original and Actual Source, Error Messages, Error Messages
+@node The Parts of the Error Message
@comment node-name, next, previous, up
@subsection The Parts of the Error Message
When processing this program, the compiler will produce this warning:
@example
-file: /tmp/foo.lisp
-
-in: DEFUN FOO
-(ZOQ Y)
---> ROQ PLOQ +
-==>
-Y
-caught WARNING:
-Result is a SYMBOL, not a NUMBER.
+; file: /tmp/foo.lisp
+; in: DEFUN FOO
+; (ZOQ Y)
+; --> ROQ PLOQ
+; ==>
+; (+ Y 3)
+;
+; caught WARNING:
+; Asserted type NUMBER conflicts with derived type (VALUES SYMBOL &OPTIONAL).
@end example
In this example we see each of the six possible parts of a compiler
@enumerate
@item
-@samp{File: /tmp/foo.lisp} This is the name of the file that the
+@findex with-compilation-unit
+@samp{file: /tmp/foo.lisp} This is the name of the file that the
compiler read the relevant code from. The file name is displayed
because it may not be immediately obvious when there is an error
during compilation of a large system, especially when
@code{foo}.
@item
+@cindex Original Source
@samp{(ZOQ Y)} This is the @dfn{original source} form responsible for
the error. Original source means that the form directly appeared in
the original input to the compiler, i.e. in the lambda passed to
for the error.
@item
-@samp{--> ROQ PLOQ +} This is the @dfn{processing path} that the
+@cindex Processing Path
+@samp{--> ROQ PLOQ} This is the @dfn{processing path} that the
compiler used to produce the errorful code. The processing path is a
representation of the evaluated forms enclosing the actual source that
the compiler encountered when processing the original source. The
path is the first element of each form, or the form itself if the form
is not a list. These forms result from the expansion of macros or
source-to-source transformation done by the compiler. In this
-example, the enclosing evaluated forms are the calls to @code{roq},
-@code{ploq} and @code{+}. These calls resulted from the expansion of
-the @code{zoq} macro.
+example, the enclosing evaluated forms are the calls to @code{roq} and
+@code{ploq}. These calls resulted from the expansion of the
+@code{zoq} macro.
@item
-@samp{==> Y} This is the @dfn{actual source} responsible for the
+@cindex Actual Source
+@samp{==> (+ Y 3)} This is the @dfn{actual source} responsible for the
error. If the actual source appears in the explanation, then we print
the next enclosing evaluated form, instead of printing the actual
source twice. (This is the form that would otherwise have been the
with the evaluation of the reference to the variable @code{y}.
@item
-@samp{caught WARNING: Result is a SYMBOL, not a NUMBER.} This is the
-@dfn{explanation} of the problem. In this example, the problem is that
-@code{y} evaluates to a symbol, but is in a context where a number is
-required (the argument to @code{+}).
+@samp{caught WARNING: Asserted type NUMBER conflicts with derived type
+(VALUES SYMBOL &OPTIONAL).} This is the @dfn{explanation} of the
+problem. In this example, the problem is that, while the call to
+@code{+} requires that its arguments are all of type @code{number},
+the compiler has derived that @code{y} will evaluate to a
+@code{symbol}. Note that @samp{(VALUES SYMBOL &OPTIONAL)} expresses
+that @code{y} evaluates to precisely one value.
@end enumerate
@item
The actual source form is indented like the original source, but is
marked by a preceding @samp{==>} line.
-
+@comment no it isn't.
@item
The explanation is prefixed with the error severity, which can be
first. For example:
@example
-file: /tmp/foo.lisp
-
-in: DEFUN FOO
-(ZOQ Y)
---> ROQ
-==>
-(PLOQ (+ Y 3))
-caught STYLE-WARNING:
-undefined function: PLOQ
-
-==>
-(ROQ (PLOQ (+ Y 3)))
-caught STYLE-WARNING:
-undefined function: ROQ
+; file: /tmp/foo.lisp
+; in: DEFUN FOO
+; (ZOQ Y)
+; --> ROQ
+; ==>
+; (PLOQ (+ Y 3))
+;
+; caught STYLE-WARNING:
+; undefined function: PLOQ
+
+; ==>
+; (ROQ (PLOQ (+ Y 3)))
+;
+; caught STYLE-WARNING:
+; undefined function: ROQ
@end example
+@comment fixing that weird blank line might be good
In this example, the file, definition and original source are
identical for the two messages, so the compiler omits them in the
processing path will also be omitted.
-@node The Original and Actual Source, Error Severity, The Parts of the Error Message, Error Messages
+@node The Original and Actual Source
@comment node-name, next, previous, up
@subsection The Original and Actual Source
+@cindex Original Source
+@cindex Actual Source
The @emph{original source} displayed will almost always be a list. If
the actual source for an error message is a symbol, the original
gives this error message
@example
-in: DEFUN BAR
-(LET (A) (DECLARE (FIXNUM A)) (SETQ A (FOO X)) A)
-caught WARNING: The binding of A is not a FIXNUM:
-NIL
+; file: /tmp/foo.lisp
+; in: DEFUN BAR
+; (LET (A)
+; (DECLARE (FIXNUM A))
+; (SETQ A (FOO X))
+; A)
+;
+; caught WARNING:
+; Asserted type FIXNUM conflicts with derived type (VALUES NULL &OPTIONAL).
@end example
This error message is not saying ``there is a problem somewhere in
Compiling results in this error message:
@example
-in: DEFUN FOO
-(DOTIMES (I N *UNDEFINED*))
---> DO BLOCK LET TAGBODY RETURN-FROM
-==>
-(PROGN *UNDEFINED*)
-caught STYLE-WARNING:
-undefined variable: *UNDEFINED*
+; in: DEFUN FOO
+; (DOTIMES (I N *UNDEFINED*))
+; --> DO BLOCK LET TAGBODY RETURN-FROM
+; ==>
+; (PROGN *UNDEFINED*)
+;
+; caught WARNING:
+; undefined variable: *UNDEFINED*
@end example
Note that @code{do} appears in the processing path. This is because
explanation, so the compiler backed out one level.
-@node Error Severity, Errors During Macroexpansion, The Original and Actual Source, Error Messages
+@node Error Severity
@comment node-name, next, previous, up
@subsection Error Severity
@cindex Severity of compiler errors
@cindex compiler error severity
+@tindex error
+@tindex warning
+@tindex style-warning
+@tindex compiler-note
+@tindex code-deletion-note
There are four levels of compiler error severity: @emph{error},
@emph{warning}, @emph{style warning}, and @emph{note}. The first three
@code{compile} and @code{compile-file} functions. These levels of
compiler error severity occur when the compiler handles conditions of
these classes. The fourth level of compiler error severity,
-@emph{note}, is used for problems which are too mild for the standard
-condition classes, typically hints about how efficiency might be
-improved.
+@emph{note}, corresponds to the @code{sb-ext:compiler-note}, and is
+used for problems which are too mild for the standard condition
+classes, typically hints about how efficiency might be improved. The
+@code{sb-ext:code-deletion-note}, a subtype of @code{compiler-note},
+is signalled when the compiler deletes user-supplied code, usually
+after proving that the code in question is unreachable.
+@include condition-sb-ext-compiler-note.texinfo
+@include condition-sb-ext-code-deletion-note.texinfo
-@node Errors During Macroexpansion, Read Errors, Error Severity, Error Messages
+@node Errors During Macroexpansion
@comment node-name, next, previous, up
@subsection Errors During Macroexpansion
@cindex Macroexpansion, errors during
gives this error:
@example
-in: DEFUN FOO
-(DO ((CURRENT L #) (# NIL)) (WHEN (EQ # E) (RETURN CURRENT)) )
-caught ERROR:
-(in macroexpansion of (DO # #))
-(hint: For more precise location, try *BREAK-ON-SIGNALS*.)
-DO step variable is not a symbol: (ATOM CURRENT)
+; in: DEFUN FOO
+; (DO ((CURRENT L (CDR CURRENT))
+; ((ATOM CURRENT) NIL))
+; (WHEN (EQ (CAR CURRENT) E) (RETURN CURRENT)))
+;
+; caught ERROR:
+; (in macroexpansion of (DO # #))
+; (hint: For more precise location, try *BREAK-ON-SIGNALS*.)
+; DO step variable is not a symbol: (ATOM CURRENT)
@end example
-@node Read Errors, , Errors During Macroexpansion, Error Messages
+@node Read Errors
@comment node-name, next, previous, up
@subsection Read Errors
@cindex Read errors, compiler
-SBCL's compiler (unlike CMUCL's) does not attempt to recover from read
-errors when reading a source file, but instead just reports the
-offending character position and gives up on the entire source file.
+SBCL's compiler does not attempt to recover from read errors when
+reading a source file, but instead just reports the offending
+character position and gives up on the entire source file.
@c <!-- FIXME: How much control over error messages is in SBCL?
@c _ -->
-@node Handling of Types, Compiler Policy, Error Messages, The Compiler
+@node Handling of Types
@comment node-name, next, previous, up
@section The Compiler's Handling of Types
(@pxref{Efficiency}), the use of appropriate type declarations can be
very important for performance as well.
-The SBCL compiler, like the related compiler in CMUCL, treats type
-declarations much differently than other Lisp compilers. By default
-(@emph{i.e.}, at ordinary levels of the @code{safety} compiler
-optimization parameter), the compiler doesn't blindly believe most
-type declarations; it considers them assertions about the program that
-should be checked.
+@findex safety
+The SBCL compiler treats type declarations differently from most other
+Lisp compilers. By default (@emph{i.e.}, at ordinary levels of the
+@code{safety} compiler optimization parameter), the compiler doesn't
+blindly believe most type declarations; it considers them assertions
+about the program that should be checked.
+@findex satisfies
The SBCL compiler also has a greater knowledge of the
Common Lisp type system than other compilers. Support is incomplete
-only for the @code{not}, @code{and} and @code{satisfies}
-types.
+only for types involving the @code{satisfies} type specifier.
@c <!-- FIXME: See also sections \ref{advanced-type-stuff}
@c and \ref{type-inference}, once we snarf them from the
@c CMU CL manual. -->
+@c Also see my paper on improving Baker, when I get round to it.
@menu
* Type Errors at Compile Time::
@end menu
-@node Type Errors at Compile Time, Precise Type Checking, Handling of Types, Handling of Types
+@node Type Errors at Compile Time
@comment node-name, next, previous, up
@subsection Type Errors at Compile Time
@cindex Compile time type errors
Compilation produces this warning:
@example
-in: DEFUN RAZ
-(CASE FOO (:THIS 13) (:THAT 9) (:THE-OTHER 42))
---> LET COND IF COND IF COND IF
-==>
-(COND)
-caught WARNING: This is not a FIXNUM:
-NIL
+; in: DEFUN RAZ
+; (CASE FOO (:THIS 13) (:THAT 9) (:THE-OTHER 42))
+; --> LET COND IF COND IF COND IF
+; ==>
+; (COND)
+;
+; caught WARNING:
+; This is not a FIXNUM:
+; NIL
@end example
In this case, the warning means that if @code{foo} isn't any of
executed), so it compiles the erroneous code (which will always signal
an error if it is executed) and gives a warning.
-
Type warnings are inhibited when the @code{sb-ext:inhibit-warnings}
optimization quality is @code{3}. @xref{Compiler Policy}. This
can be used in a local declaration to inhibit type warnings in a code
fragment that has spurious warnings.
-@node Precise Type Checking, Weakened Type Checking, Type Errors at Compile Time, Handling of Types
+@node Precise Type Checking
@comment node-name, next, previous, up
@subsection Precise Type Checking
@cindex Precise type checking
@code{member}, and other list-style type specifiers.
-@node Weakened Type Checking, Getting Existing Programs to Run, Precise Type Checking, Handling of Types
+@node Weakened Type Checking
@comment node-name, next, previous, up
@subsection Weakened Type Checking
@cindex Weakened type checking
nonexistent runtime checking.
-@node Getting Existing Programs to Run, Implementation Limitations, Weakened Type Checking, Handling of Types
+@node Getting Existing Programs to Run
@comment node-name, next, previous, up
@subsection Getting Existing Programs to Run
@cindex Existing programs, to run
@cindex Compatibility with other Lisps
@c (should also have an entry in the non-ANSI-isms section)-->
-Since SBCL's compiler, like CMUCL's compiler, does much more
-comprehensive type checking than most Lisp compilers, SBCL may detect
-type errors in programs that have been debugged using other
-compilers. These errors are mostly incorrect declarations, although
-compile-time type errors can find actual bugs if parts of the program
-have never been tested.
+Since SBCL's compiler does much more comprehensive type checking than
+most Lisp compilers, SBCL may detect type errors in programs that have
+been debugged using other compilers. These errors are mostly incorrect
+declarations, although compile-time type errors can find actual bugs
+if parts of the program have never been tested.
Some incorrect declarations can only be detected by run-time type
checking. It is very important to initially compile a program with
@c <!-- FIXME: <xref>ND-variables, once we crib the text from the
@c CMU CL manual. -->
-@node Implementation Limitations, , Getting Existing Programs to Run, Handling of Types
+@node Implementation Limitations
@comment node-name, next, previous, up
@subsection Implementation Limitations
may, alas, remain in the system for a while.
-@node Compiler Policy, Open Coding and Inline Expansion, Handling of Types, The Compiler
+@node Compiler Policy
@comment node-name, next, previous, up
@section Compiler Policy
system.
Compiler policy is controlled by the @code{optimize} declaration. The
-compiler supports the ANSI optimization qualities, and also an
-extension @code{sb-ext:inhibit-warnings}.
+compiler supports the ANSI optimization qualities, and also a
+deprecated extension @code{sb-ext:inhibit-warnings}.
Ordinarily, when the @code{speed} quality is high, the compiler emits
notes to notify the programmer about its inability to apply various
arithmetic, which is not helpful for code which by design supports
arbitrary-sized integers instead of being limited to fixnums.)
-@quotation
-Note: The basic functionality of the @code{optimize
-inhibit-warnings} extension will probably be supported in all future
-versions of the system, but it will probably be renamed when the
-compiler and its interface are cleaned up. The current name is
-misleading, because it mostly inhibits optimization notes, not
-warnings. And making it an optimization quality is misleading, because
-it shouldn't affect the resulting code at all. It may become a
-declaration identifier with a name like
-@code{sb-ext:inhibit-notes}, so that what's currently written.
-
+The recommended way to inhibit compiler diagnostics (of any severity
+other than @code{error}: @pxref{Error Severity}) is to use the
+@code{sb-ext:muffle-conditions} declaration, specifying the type of
+condition that is to be muffled (using an associated
+@code{muffle-warning} restart). Thus, what was previously written
@lisp
(declaim (optimize (sb-ext:inhibit-warnings 2)))
@end lisp
-
-would become something like
-
+becomes something like
@lisp
-(declaim (sb-ext:inhibit-notes 2))
+(declaim (sb-ext:muffle-conditions sb-ext:compiler-note))
+@end lisp
+to muffle all compiler notes. Compiler diagnostics can be muffled in
+the lexical scope of a declaration, and also lexically unmuffled by
+the use of the sb-ext:unmuffle-conditions, for instance
+@lisp
+(defun foo (x)
+ (declare (optimize speed) (fixnum x))
+ (declare (sb-ext:muffle-conditions sb-ext:compiler-note))
+ (values (* x 5) ; no compiler note from this
+ (locally
+ (declare (sb-ext:unmuffle-conditions sb-ext:compiler-note))
+ ;; this one gives a compiler note
+ (* x -5))))
@end lisp
-
-@end quotation
In early versions of SBCL, a @code{speed} value of zero was used to
enable byte compilation, but since version 0.7.0, SBCL only supports
whether to inline operations, which tend to increase the size of
programs. Use the value @code{0} with caution, since it can cause the
compiler to inline operations so indiscriminately that the net effect
-is to slow the program by causing cache misses or swapping.
+is to slow the program by causing cache misses or even swapping.
@c <!-- FIXME: old CMU CL compiler policy, should perhaps be adapted
@c _ for SBCL. (Unfortunately, the CMU CL docs are out of sync with the
@c _-->
-@node Open Coding and Inline Expansion, , Compiler Policy, The Compiler
+@node Open Coding and Inline Expansion
@comment node-name, next, previous, up
@section Open Coding and Inline Expansion
@cindex Open-coding
redefine standard functions, users sometimes want to implicitly
redefine these functions when they are debugging using the
@code{trace} macro. Special-casing of standard functions can be
-inhibited using the @code{notinline} declaration.
+inhibited using the @code{notinline} declaration, but even then some
+phases of analysis such as type inferencing are applied by the
+compiler.
@item
The compiler can have multiple alternate implementations of standard
projects / sbcl.git / blobdiff