@setfilename gcj.info
@settitle Guide to GNU gcj
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
@include gcc-common.texi
@c Note: When reading this manual you'll find lots of strange
@ifinfo
@format
-@dircategory Programming
+@dircategory Software development
@direntry
* Gcj: (gcj). Ahead-of-time compiler for the Java language
@end direntry
Generate header files from Java class files
* gjnih: (gcj)Invoking gjnih.
Generate JNI header files from Java class files
-* jv-scan: (gcj)Invoking jv-scan.
- Print information about Java source files
* jcf-dump: (gcj)Invoking jcf-dump.
Print information about Java class files
* gij: (gcj)Invoking gij. GNU interpreter for Java bytecode
* Compatibility:: Compatibility between gcj and other tools for Java
* Invoking gcjh:: Generate header files from class files
* Invoking gjnih:: Generate JNI header files from class files
-* Invoking jv-scan:: Print information about source files
* Invoking jcf-dump:: Print information about class files
* Invoking gij:: Interpreting Java bytecodes
* Invoking gcj-dbtool:: Tool for manipulating class file databases.
* About CNI:: Description of the Compiled Native Interface
* System properties:: Modifying runtime behavior of the libgcj library
* Resources:: Where to look for more information
+* Index:: Index.
@end menu
@var{sourcefile}@dots{}
@c man end
@c man begin SEEALSO gcj
-gcc(1), gcjh(1), gjnih(1), gij(1), jv-scan(1), jcf-dump(1), gfdl(7),
+gcc(1), gcjh(1), gjnih(1), gij(1), jcf-dump(1), gfdl(7),
and the Info entries for @file{gcj} and @file{gcc}.
@c man end
@end ignore
This forces the compiler to always check for the special zero length
attribute @code{gnu.gcj.gcj-compiled} in @code{java.lang.Object} and
issue an error if it isn't found.
+
+@item -fsource=@var{VERSION}
+This option is used to choose the source version accepted by
+@command{gcj}. The default is @samp{1.5}.
@end table
@node Encodings
of the @code{gij} command.
This option is an alternative to using @code{--main}; you cannot use both.
+
+@item -static-libgcj
+This option causes linking to be done against a static version of the
+libgcj runtime library. This option is only available if
+corresponding linker support exists.
+
+@strong{Caution:} Static linking of libgcj may cause essential parts
+of libgcj to be omitted. Some parts of libgcj use reflection to load
+classes at runtime. Since the linker does not see these references at
+link time, it can omit the referred to classes. The result is usually
+(but not always) a @code{ClassNotFoundException} being thrown at
+runtime. Caution must be used when using this option. For more
+details see:
+@w{@uref{http://gcc.gnu.org/wiki/Statically%20linking%20libgcj}}
@end table
@node Code Generation
The actual file name to be compiled this way must be specified
separately.
+@item -ftarget=@var{VERSION}
+This can be used with @option{-C} to choose the version of bytecode
+emitted by @command{gcj}. The default is @samp{1.5}. When not
+generating bytecode, this option has no effect.
+
@item -d @var{directory}
When used with @code{-C}, this causes all generated @file{.class} files
to be put in the appropriate subdirectory of @var{directory}. By
@code{Class.forName()} will search @samp{CLASSPATH} to find the
desired class.
+@item -freduced-reflection
+This option causes the code generated by @command{gcj} to contain a
+reduced amount of the class meta-data used to support runtime
+reflection. The cost of this savings is the loss of
+the ability to use certain reflection capabilities of the standard
+Java runtime environment. When set all meta-data except for that
+which is needed to obtain correct runtime semantics is eliminated.
+
+For code that does not use reflection (i.e. the methods in the
+@code{java.lang.reflect} package), @code{-freduced-reflection}
+will result in proper operation with a savings in executable code size.
+
+JNI (@code{-fjni}) and the binary compatibility ABI
+(@code{-findirect-dispatch}) do not work properly without full
+reflection meta-data. Because of this, it is an error to use these options
+with @code{-freduced-reflection}.
+
+@strong{Caution:} If there is no reflection meta-data, code that uses
+a @code{SecurityManager} may not work properly. Also calling
+@code{Class.forName()} may fail if the calling method has no
+reflection meta-data.
+
@end table
@xref{About CNI}, for more info on how to use this in your programs.
@item
-When you compile your classes into a shared library they can be automatically
-loaded by the @code{libgcj} system classloader. When trying to load a class
-@code{gnu.pkg.SomeClass} the system classloader will first try to load the
-shared library @file{lib-gnu-pkg-SomeClass.so}, if that fails to load the
-class then it will try to load @file{lib-gnu-pkg.so} and finally when the
-class is still not loaded it will try to load @file{lib-gnu.so}. Note that
+When you compile your classes into a shared library using
+@code{-findirect-dispatch} then add them to the system-wide
+classmap.db file using @code{gcj-dbtool}, they will be automatically
+loaded by the @code{libgcj} system classloader. This is the new,
+preferred classname-to-library resolution mechanism. @xref{Invoking
+gcj-dbtool}, for more information on using the classmap database.
+
+@item
+The old classname-to-library lookup mechanism is still supported
+through the @code{gnu.gcj.runtime.VMClassLoader.library_control}
+property, but it is deprecated and will likely be removed in some
+future release. When trying to load a class @code{gnu.pkg.SomeClass}
+the system classloader will first try to load the shared library
+@file{lib-gnu-pkg-SomeClass.so}, if that fails to load the class then
+it will try to load @file{lib-gnu-pkg.so} and finally when the class
+is still not loaded it will try to load @file{lib-gnu.so}. Note that
all @samp{.}s will be transformed into @samp{-}s and that searching
-for inner classes starts with their outermost outer class. If the class
-cannot be found this way the system classloader tries to use
-the @code{libgcj} bytecode interpreter to load the class from the standard
+for inner classes starts with their outermost outer class. If the
+class cannot be found this way the system classloader tries to use the
+@code{libgcj} bytecode interpreter to load the class from the standard
classpath. This process can be controlled to some degree via the
@code{gnu.gcj.runtime.VMClassLoader.library_control} property;
@xref{libgcj Runtime Properties}.
gcjh [@option{-stubs}] [@option{-jni}]
[@option{-force}] [@option{-old}] [@option{-trace}] [@option{-J} @var{option}]
[@option{-add} @var{text}] [@option{-append} @var{text}] [@option{-friend} @var{text}]
- [@option{-preprend} @var{text}]
+ [@option{-prepend} @var{text}]
[@option{--classpath}=@var{path}] [@option{--CLASSPATH}=@var{path}]
[@option{--bootclasspath}=@var{path}]
[@option{-I}@var{dir}@dots{}] [@option{-d} @var{dir}@dots{}]
@var{classname}@dots{}
@c man end
@c man begin SEEALSO gcjh
-gcc(1), gcj(1), gij(1), jv-scan(1), jcf-dump(1), gfdl(7),
+gcc(1), gcj(1), gij(1), jcf-dump(1), gfdl(7),
and the Info entries for @file{gcj} and @file{gcc}.
@c man end
@end ignore
gjnih [@option{-stubs}] [@option{-jni}]
[@option{-force}] [@option{-old}] [@option{-trace}] [@option{-J} @var{option}]
[@option{-add} @var{text}] [@option{-append} @var{text}] [@option{-friend} @var{text}]
- [@option{-preprend} @var{text}]
+ [@option{-prepend} @var{text}]
[@option{--classpath}=@var{path}] [@option{--CLASSPATH}=@var{path}]
[@option{--bootclasspath}=@var{path}]
[@option{-I}@var{dir}@dots{}] [@option{-d} @var{dir}@dots{}]
@var{classname}@dots{}
@c man end
@c man begin SEEALSO gjnih
-gcc(1), gcj(1), gcjh(1), gij(1), jv-scan(1), jcf-dump(1), gfdl(7),
+gcc(1), gcj(1), gcjh(1), gij(1), jcf-dump(1), gfdl(7),
and the Info entries for @file{gcj} and @file{gcc}.
@c man end
@end ignore
@c man end
-@node Invoking jv-scan
-@chapter Invoking jv-scan
-
-@c man title jv-scan print information about Java source file
-
-@c man begin DESCRIPTION jv-scan
-
-The @code{jv-scan} program can be used to print information about a Java
-source file (@file{.java} file).
-
-@c man end
-
-@ignore
-@c man begin SYNOPSIS jv-scan
-jv-scan [@option{--no-assert}] [@option{--complexity}]
- [@option{--encoding}=@var{name}] [@option{--print-main}]
- [@option{--list-class}] [@option{--list-filename}]
- [@option{--version}] [@option{--help}]
- [@option{-o} @var{file}] @var{inputfile}@dots{}
-@c man end
-@c man begin SEEALSO jv-scan
-gcc(1), gcj(1), gcjh(1), gij(1), jcf-dump(1), gfdl(7),
-and the Info entries for @file{gcj} and @file{gcc}.
-@c man end
-@end ignore
-
-@c man begin OPTIONS jv-scan
-
-@table @gcctabopt
-@item --no-assert
-Don't recognize the @code{assert} keyword, for backwards compatibility
-with older versions of the language specification.
-
-@item --complexity
-This prints a complexity measure, related to cyclomatic complexity, for
-each input file.
-
-@item --encoding=@var{name}
-This works like the corresponding @command{gcj} option.
-
-@item --print-main
-This prints the name of the class in this file containing a @code{main}
-method.
-
-@item --list-class
-This lists the names of all classes defined in the input files.
-
-@item --list-filename
-If @code{--list-class} is given, this option causes @code{jv-scan} to
-also print the name of the file in which each class was found.
-
-@item -o @var{file}
-Print output to the named file.
-
-@item --help
-Print help, then exit.
-
-@item --version
-Print version number, then exit.
-@end table
-
-@c man end
-
@node Invoking jcf-dump
@chapter Invoking jcf-dump
[@option{--showversion}] [@option{--version}] [@option{--help}][@option{-?}]
@c man end
@c man begin SEEALSO gij
-gcc(1), gcj(1), gcjh(1), jv-scan(1), jcf-dump(1), gfdl(7),
+gcc(1), gcj(1), gcjh(1), jcf-dump(1), gfdl(7),
and the Info entries for @file{gcj} and @file{gcc}.
@c man end
@end ignore
@item -Xmx@var{size}
Set the maximum heap size.
+
+@item -Xss@var{size}
+Set the thread stack size.
@end table
Unrecognized @code{-X} options are ignored, for compatibility with
@c man end
@c man begin SEEALSO gij
-gcc(1), gcj(1), gcjh(1), jv-scan(1), jcf-dump(1), gfdl(7),
+gcc(1), gcj(1), gcjh(1), jcf-dump(1), gfdl(7),
and the Info entries for @file{gcj} and @file{gcc}.
@c man end
@end ignore
@menu
* Basic concepts:: Introduction to using CNI@.
* Packages:: How packages are mapped to C++.
-* Primitive types:: Handling Java types in C++.
+* Primitive types:: Handling primitive Java types in C++.
+* Reference types:: Handling Java reference types in C++.
* Interfaces:: How Java interfaces map to C++.
* Objects and Classes:: C++ and Java classes.
* Class Initialization:: How objects are initialized.
@subsection Reference types associated with primitive types
In Java each primitive type has an associated reference type,
-e.g.: @code{boolean} has an associated @code{java.lang.Boolean} class.
+e.g.: @code{boolean} has an associated @code{java.lang.Boolean.TYPE} class.
In order to make working with such classes easier GCJ provides the macro
@code{JvPrimClass}:
@end deffn
+@node Reference types
+@section Reference types
+
+A Java reference type is treated as a class in C++. Classes and
+interfaces are handled this way. A Java reference is translated to a
+C++ pointer, so for instance a Java @code{java.lang.String} becomes,
+in C++, @code{java::lang::String *}.
+
+CNI provides a few built-in typedefs for the most common classes:
+@multitable @columnfractions .30 .25 .60
+@item @strong{Java type} @tab @strong{C++ typename} @tab @strong{Description}
+@item @code{java.lang.Object} @tab @code{jobject} @tab Object type
+@item @code{java.lang.String} @tab @code{jstring} @tab String type
+@item @code{java.lang.Class} @tab @code{jclass} @tab Class type
+@end multitable
+@cindex jobject
+@cindex jstring
+@cindex jclass
+
+Every Java class or interface has a corresponding @code{Class}
+instance. These can be accessed in CNI via the static @code{class$}
+field of a class. The @code{class$} field is of type @code{Class}
+(and not @code{Class *}), so you will typically take the address of
+it.
+@cindex class$
+
+Here is how you can refer to the class of @code{String}, which in
+Java would be written @code{String.class}:
+
+@example
+using namespace java::lang;
+doSomething (&String::class$);
+@end example
+
+
@node Interfaces
@section Interfaces
@deftypefun jobjectArray JvNewObjectArray (jsize @var{length}, jclass @var{klass}, jobject @var{init})
-Here @code{klass} is the type of elements of the array and
+This creates a new array whose elements have reference type.
+@code{klass} is the type of elements of the array and
@code{init} is the initial value put into every slot in the array.
@end deftypefun
+@example
+using namespace java::lang;
+JArray<String *> *array
+ = (JArray<String *> *) JvNewObjectArray(length, &String::class$, NULL);
+@end example
+
@subsection Creating arrays
@noindent The following function definition is the template for all such functions:
@deftypefun jbooleanArray JvNewBooleanArray (jint @var{length})
-Create's an array @var{length} indices long.
+Creates an array @var{length} indices long.
@end deftypefun
@deftypefun jsize JvGetArrayLength (jarray @var{array})
is wrapped with a try/catch block to provide a default handler for any uncaught
exceptions.
-The example can be compiled with @command{c++ test.cc -lgcj}.
+The example can be compiled with @command{c++ -c test.cc; gcj test.o}.
@example
// test.cc
#include <java/io/PrintStream.h>
#include <java/lang/Throwable.h>
-int main(int argc, char *argv)
+int main(int argc, char *argv[])
@{
using namespace java::lang;
string. Only used when running a debug build of the library.
@item gnu.classpath.vm.shortname
-This is a succint name of the virtual machine. For @code{libgcj},
+This is a succinct name of the virtual machine. For @code{libgcj},
this will always be @samp{libgcj}.
@item gnu.classpath.home.url
used, or the program binary name in the case where an application is compiled
to a native binary.
+@item gnu.gcj.user.realname
+The real name of the user, as taken from the password file. This may
+not always hold only the user's name (as some sites put extra
+information in this field). Also, this property is not available on
+all platforms.
+
@item gnu.gcj.runtime.NameFinder.use_addr2line
Whether an external process, @command{addr2line}, should be used to determine
line number information when tracing the stack. Setting this to @code{false}
significantly for applications that print stack traces or make logging calls
frequently.
+@item gnu.gcj.runtime.NameFinder.show_raw
+Whether the address of a stack frame should be printed when the line
+number is unavailable. Setting this to @code{true} will cause the name
+of the object and the offset within that object to be printed when no
+line number is available. This allows for off-line decoding of
+stack traces if necessary debug information is available. The default
+is @code{false}, no raw addresses are printed.
+
+@item gnu.gcj.runtime.NameFinder.remove_unknown
+Whether stack frames for non-java code should be included in a stack
+trace. The default value is @code{true}, stack frames for non-java
+code are suppressed. Setting this to @code{false} will cause any
+non-java stack frames to be printed in addition to frames for the java
+code.
+
@item gnu.gcj.runtime.VMClassLoader.library_control
This controls how shared libraries are automatically loaded by the
built-in class loader. If this property is set to @samp{full}, a full
search is done for each requested class. If this property is set to
-@samp{cache} (the default), then any failed lookups are cached and not
-tried again. If this property is set to @samp{never}, then lookups
+@samp{cache}, then any failed lookups are cached and not tried again.
+If this property is set to @samp{never} (the default), then lookups
are never done. For more information, @xref{Extensions}.
@item gnu.gcj.runtime.endorsed.dirs
because the JCK is not free. See
@uref{http://sources.redhat.com/mauve/} for more information.
+
+@node Index
+@unnumbered Index
+
+@printindex cp
+
@bye
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