The scl values are defined in binutils-gdb/include/coff/internal.h:

/********************** STORAGE CLASSES **********************/ /* This used to be defined as -1, but now n_sclass is unsigned. */ #define C_EFCN 0xff /* physical end of function */ #define C_NULL 0 #define C_AUTO 1 /* automatic variable */ #define C_EXT 2 /* external symbol */ #define C_STAT 3 /* static */ #define C_REG 4 /* register variable */ #define C_EXTDEF 5 /* external definition */ #define C_LABEL 6 /* label */ #define C_ULABEL 7 /* undefined label */ #define C_MOS 8 /* member of structure */ #define C_ARG 9 /* function argument */ #define C_STRTAG 10 /* structure tag */ #define C_MOU 11 /* member of union */ #define C_UNTAG 12 /* union tag */ #define C_TPDEF 13 /* type definition */ #define C_USTATIC 14 /* undefined static */ #define C_ENTAG 15 /* enumeration tag */ #define C_MOE 16 /* member of enumeration */ #define C_REGPARM 17 /* register parameter */ #define C_FIELD 18 /* bit field */ #define C_AUTOARG 19 /* auto argument */ #define C_LASTENT 20 /* dummy entry (end of block) */ #define C_BLOCK 100 /* ".bb" or ".eb" */ #define C_FCN 101 /* ".bf" or ".ef" */ #define C_EOS 102 /* end of structure */ #define C_FILE 103 /* file name */ #define C_LINE 104 /* line # reformatted as symbol table entry */ #define C_ALIAS 105 /* duplicate tag */ #define C_HIDDEN 106 /* ext symbol in dmert public lib */ #define C_WEAKEXT 127 /* weak symbol -- GNU extension. */ /* New storage classes for TI COFF */ #define C_UEXT 19 /* Tentative external definition */ #define C_STATLAB 20 /* Static load time label */ #define C_EXTLAB 21 /* External load time label */ #define C_SYSTEM 23 /* System Wide variable */ /* New storage classes for WINDOWS_NT */ #define C_SECTION 104 /* section name */ #define C_NT_WEAK 105 /* weak external */ /* New storage classes for 80960 */ /* C_LEAFPROC is obsolete. Use C_LEAFEXT or C_LEAFSTAT */ #define C_LEAFPROC 108 /* Leaf procedure, "call" via BAL */ #define C_SCALL 107 /* Procedure reachable via system call */ #define C_LEAFEXT 108 /* External leaf */ #define C_LEAFSTAT 113 /* Static leaf */ #define C_OPTVAR 109 /* Optimized variable */ #define C_DEFINE 110 /* Preprocessor #define */ #define C_PRAGMA 111 /* Advice to compiler or linker */ #define C_SEGMENT 112 /* 80960 segment name */ /* New storage classes for RS/6000 */ #define C_HIDEXT 107 /* Un-named external symbol */ #define C_BINCL 108 /* Marks beginning of include file */ #define C_EINCL 109 /* Marks ending of include file */ #define C_AIX_WEAKEXT 111 /* AIX definition of C_WEAKEXT. */ #define C_DWARF 112 /* DWARF symbol */ 

So "scl 3" means that the variable is static and "scl 2" means that it is extern.