While investigating a different issue, I found what I think is a problem with GPC's enforcement of Extended Pascal's actual parameter requirements for formal protected var parameters. The problem is that GPC allows function-access expressions to be used as the actual parameter for a formal protected var parameter and the function-access isn't a variable-access as required by Extended Pascal.
For formal variable parameters, Extended Pascal requires the actual-parameter ... "shall be variable-access" (see paragraph 6.7.3.3) regardless of whether 'protected' is used in the formal parameter declaration. ('Protected' does not change the requirements for the actual-parameter. It just requires that no statements within the procedure/function shall threaten a protected formal-parameter identifier.)
While GPC doesn't allow function-access expression actual-parameters for non-protected formal variable parameters, it incorrectly allows function-access expression actual-parameters to be used for protected formal variable parameters. A short test program that demonstrates the problem:
{$extended-pascal} program ProtectVarParameterTest(input, output);
var globalInt : Integer;
function GetInteger: Integer; begin GetInteger := 1; end;
procedure DoSomethingProtectedVar(protected var anInt : Integer); begin globalInt := anInt; end;
procedure DoSomethingVar(var anInt : Integer); begin globalInt := anInt; end;
begin globalInt := 0; DoSomethingProtectedVar(GetInteger); {WRONG} writeln('FAIL'); {DoSomethingVar(GetInteger); writeln('FAIL');} end.
With the last two statements commented out, GPC compiles the program with no errors and running the compiled program produces and output of: FAIL.
Uncommenting out the last two statements, GPC doesn't compile the program and generates error messages:
ProtectVarParameterTest.pas: In main program: ProtectVarParameterTest.pas:26: error: type mismatch in argument 1 of `DoSomethingVar' ProtectVarParameterTest.pas:18: error: routine declaration
(Note - the error messages in this test example are pretty obtuse. In the program where I initial found the problem, the error message of "error: reference expected, value given" is much clearer as to what the real cause of the problem is.)
The command line and compiler information used on both versions of the test program were:
gpc --automake -v ProtectVarParameterTest.pas -o ProtectVarParameterTest Reading specs from /Developer/Pascal/gpc33d6/lib/gcc-lib/powerpc-apple-darwin/3.3/specs Configured with: ../gpc-3.3d6/configure --enable-languages=pascal,c --enable-threads=posix --prefix=/Developer/Pascal/gpc33d6 --target=powerpc-apple-darwin Thread model: posix gpc version 20030507, based on gcc-3.3 /Developer/Pascal/gpc33d6/lib/gcc-lib/powerpc-apple-darwin/3.3/gpcpp -D__BITS_BIG_ENDIAN__=1 -D__BYTES_BIG_ENDIAN__=1 -D__WORDS_BIG_ENDIAN__=1 -D__NEED_NO_ALIGNMENT__=1 -quiet -v -iprefix /usr/bin/../lib/gcc-lib/powerpc-apple-darwin/3.3/ -D__GNUC__=3 -D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=0 -D__DYNAMIC__ ProtectVarParameterTest.pas -fautomake -famtmpfile=/var/tmp//cc2sio8x.gpa /var/tmp//ccmxZG89.i GNU Pascal Compiler PreProcessor version 20030507, based on gcc-3.3 (Darwin/PowerPC) /Developer/Pascal/gpc33d6/lib/gcc-lib/powerpc-apple-darwin/3.3/gpc1 /var/tmp//ccmxZG89.i -fPIC -quiet -dumpbase ProtectVarParameterTest.pas -auxbase ProtectVarParameterTest -version -fautomake -famtmpfile=/var/tmp//cc2sio8x.gpa -o /var/tmp//ccPyvMwU.s GNU Pascal version is actually 20030507, based on gcc-3.3 GNU Pascal version 3.3 (powerpc-apple-darwin) compiled by GNU C version 3.3. GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Gale Paeper gpaeper@empirenet.com