GCC developers: Is there dwarf information that gives the size of a variable? I have a test case which when run on Intel gdb can print the size of an optimized out variable. However on PowerPC, gdb says the size information for the variable is optimized out. Is there some DWARF information that I can print on the Intel binary that shows the size information for the variable even though the variable is optimized out? Then by comparison on PowerPC I would expect the DWARF information would either say the size of the variable is optimized out or there is no information available.
Here is the test program for the test. #include "../lib/attributes.h" int #ifdef NOCLONE __attribute__((noinline,weak)) ATTRIBUTE_NOCLONE #else __attribute__((noinline,weak)) #endif f1 (int i) { char a[i + 1]; a[0] = 5; return a[0]; } int main (void) { volatile int j; int i = 5; asm volatile ("" : "=r" (i) : "0" (i)); j = f1 (i); return 0; } So when the above test program is compiled with -03 and run on Intel we have the following: (gdb) break f1 Breakpoint 1 at 0x1150: file /.../gdb/testsuite/gdb.base/vla-optimized-out.c, line 30. (gdb) r Starting program: /.../gdb/testsuite/outputs/gdb.base/vla-optimized-out/vla-optimized-out-o3 [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". Breakpoint 1, f1 (i=5) at /.../gdb/testsuite/gdb.base/vla-optimized-out.c:30 30 { (gdb) p a $1 = <optimized out> (gdb) p sizeof( a) $2 = 6 <- the variable is optimized out but apparently the size info is still accessible When I compile and run the same program on PowerPC: (gdb) break f1 Breakpoint 1 at 0x100006e0: file /.../gdb/testsuite/gdb.base/vla-optimized-out.c, line 33. (gdb) r Starting program: /home/carll/GDB/build-current/.../vla-optimized-out-3 [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib64/libthread_db.so.1". Breakpoint 1, f1 (i=5) at /.../gdb/testsuite/gdb.base/vla-optimized-out.c:33 33 return a[0]; (gdb) p a $1 = <optimized out> (gdb) p sizeof (a) $2 = <optimized out> <- the variable is optimized out and the size is not available. Anyway, I am looking for some DWARF info on Intel and PowerPC which will show why Intel can display the size of the variable but PowerPC can not. Thanks for you help. Carl Love