For what it is worth, here is a list of warnings produced when compiling MonetDB/SQL. MonetDB itself appears to be mostly warning free.
Making and installing MonetDB/SQL in /ufs/fabian/scratch/vtmp/build-current-monetdb-pegasus.ins.cwi.nl/sql /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_table.mx: In function 'table_delete': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_table.mx:223: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_table.mx: In function 'table_check': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_table.mx:266: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'schema_get_table': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:1177: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_kc': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4069: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_key': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4084: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_ic': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4113: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_idx': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4128: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_tc': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4151: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_trigger': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4165: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_column': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4187: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_table': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4240: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sys_drop_func': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4264: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4265: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sql_trans_drop_schema': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4413: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sql_trans_alter_null': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4717: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx: In function 'sql_trans_alter_default': /ufs/fabian/scratch/monetdb/current/sql/src/storage/bat/bat_store.mx:4741: warning: comparison between signed and unsigned sql_parser.y:404.8-12: warning: symbol CHECK redeclared sql_parser.y:408.16-23: warning: symbol DISTINCT redeclared sql_parser.y:410.41-46: warning: symbol HAVING redeclared conflicts: 21 shift/reduce, 44 reduce/reduce sql_parser.y:404.8-12: warning: symbol CHECK redeclared sql_parser.y:408.16-23: warning: symbol DISTINCT redeclared sql_parser.y:410.41-46: warning: symbol HAVING redeclared conflicts: 21 shift/reduce, 44 reduce/reduce /ufs/fabian/scratch/monetdb/current/sql/src/server/sql_select.mx: In function 'sql_binop': /ufs/fabian/scratch/monetdb/current/sql/src/server/sql_select.mx:924: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/server/sql_scan.mx: In function 'scanner_string': /ufs/fabian/scratch/monetdb/current/sql/src/server/sql_scan.mx:562: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/server/rel_select.mx: In function 'rel_binop': /ufs/fabian/scratch/monetdb/current/sql/src/server/rel_select.mx:2878: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx: In function 'mvc_dump_1': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:252: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx: In function 'mvc_dump_2': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:269: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx: In function 'dump_1': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:286: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx: In function 'dump_2': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:303: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx: In function 'dump_3': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:322: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx: In function 'backend_dumpstmt_': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:371: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:377: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:392: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:407: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:417: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:427: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:821: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:834: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:850: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:856: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:873: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:876: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:924: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:946: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:966: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:972: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:975: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1032: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1042: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1081: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1149: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1151: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1153: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1155: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1157: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1160: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1260: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1283: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1301: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1303: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1351: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_gencode.mx:1416: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_result.mx: In function 'convert2str': /ufs/fabian/scratch/monetdb/current/sql/src/backends/monet4/sql_result.mx:564: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/odbc/driver/ODBCConvert.c: In function 'ODBCFetch': /ufs/fabian/scratch/monetdb/current/sql/src/odbc/driver/ODBCConvert.c:1133: warning: signed and unsigned type in conditional expression /ufs/fabian/scratch/monetdb/current/sql/src/odbc/driver/ODBCConvert.c:1418: warning: signed and unsigned type in conditional expression /ufs/fabian/scratch/monetdb/current/sql/src/odbc/driver/SQLConnect.c: In function 'SQLConnect_': /ufs/fabian/scratch/monetdb/current/sql/src/odbc/driver/SQLConnect.c:93: warning: comparison between signed and unsigned /ufs/fabian/scratch/monetdb/current/sql/src/odbc/driver/SQLConnect.c:111: warning: comparison between signed and unsigned