I've installed gcc 4.2.1 and 4.3-svn in parallel, 4.2.1 as normal compiler, 4.3 with --program-suffix=-4.3 (and with contrib/download_ecj).
Trying to use gcjavac from 4.3 results in: $ gcjavac-4.3 test.java java.lang.NullPointerException at java.lang.String.<init>(libgcj.so.9) at org.eclipse.jdt.internal.compiler.batch.FileSystem.initializeKnownFileNames(FileSystem.java:192) at org.eclipse.jdt.internal.compiler.batch.FileSystem.<init>(FileSystem.java:128) at org.eclipse.jdt.internal.compiler.batch.Main.getLibraryAccess(Main.java:3271) at org.eclipse.jdt.internal.compiler.batch.Main.performCompilation(Main.java:3379) at org.eclipse.jdt.internal.compiler.batch.Main.compile(Main.java:1607) at org.eclipse.jdt.internal.compiler.batch.GCCMain.compile(GCCMain.java:474) at org.eclipse.jdt.internal.compiler.batch.GCCMain.main(GCCMain.java:491) Or, when forcing libgcj into the CLASSPATH: $ CLASSPATH=/usr/share/java/libgcj-4.3.0.jar gcjavac-4.3 test.java java.lang.ClassCastException: org.eclipse.jdt.internal.compiler.ast.MethodDeclaration cannot be cast to org.eclipse.jdt.internal.compiler.ast.AnnotationMethodDeclaration at org.eclipse.jdt.internal.compiler.parser.Parser.consumeMethodHeaderExtendedDims(Parser.java:4223) at org.eclipse.jdt.internal.compiler.parser.Parser.consumeRule(Parser.java:5184) at org.eclipse.jdt.internal.compiler.parser.Parser.parse(Parser.java:9007) at org.eclipse.jdt.internal.compiler.parser.Parser.parse(Parser.java:9238) at org.eclipse.jdt.internal.compiler.parser.Parser.parse(Parser.java:9195) at org.eclipse.jdt.internal.compiler.parser.Parser.dietParse(Parser.java:7851) at org.eclipse.jdt.internal.compiler.Compiler.internalBeginToCompile(Compiler.java:587) at org.eclipse.jdt.internal.compiler.Compiler.beginToCompile(Compiler.java:357) at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:371) at org.eclipse.jdt.internal.compiler.batch.Main.performCompilation(Main.java:3410) at org.eclipse.jdt.internal.compiler.batch.Main.compile(Main.java:1607) at org.eclipse.jdt.internal.compiler.batch.GCCMain.compile(GCCMain.java:474) at org.eclipse.jdt.internal.compiler.batch.GCCMain.main(GCCMain.java:491) org.eclipse.jdt.internal.compiler.ast.MethodDeclaration cannot be cast to org.eclipse.jdt.internal.compiler.ast.AnnotationMethodDeclaration (test.java is just a simple hello world-style app) -- Summary: [4.3 regression] gcjavac throws java exceptions on startup Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: java AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: bero at arklinux dot org GCC build triplet: i586-pc-linux-gnu GCC host triplet: i586-pc-linux-gnu GCC target triplet: i586-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32967