I havent ever seen a definition of a SV struct that allows you to easily see in a C debugger what the flags/type of an SV is. So I wrote this up. 
#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

struct pMG;
typedef struct pMG pMG;
struct pMG {
    XPVMG*    sv_any;        
    U32        sv_refcnt;
    union {
        U32        sv_flags;
        struct {
            unsigned long type : 8;
            unsigned long f_IOK : 1;
            unsigned long f_NOK : 1;
            unsigned long f_POK : 1;
            unsigned long f_ROK : 1;
            unsigned long p_IOK: 1;
            unsigned long p_NOK: 1;
            unsigned long p_POK : 1;
            unsigned long p_SCREAM_phv_CLONEABLE_phv_CLONEABLE_prv_PCS
+_IMPORTED : 1;
            unsigned long s_PADSTALE_SVpad_STATE : 1;
            unsigned long s_PADTMP_SVpad_TYPED : 1;
            unsigned long s_PADMY_SVpad_OUR : 1;
            unsigned long s_TEMP : 1;            
            unsigned long s_OBJECT : 1;
            unsigned long s_GMG : 1;
            unsigned long s_SMG : 1;
            unsigned long s_RMG : 1;
            unsigned long f_FAKE_SVphv_REHASH : 1;
            unsigned long f_OOK : 1;
            unsigned long f_BREAK: 1;
            unsigned long f_READONLY : 1;
            unsigned long f_AMAGIC : 1;
            unsigned long f_UTF8_SVphv_SHAREKEYS : 1;
            unsigned long pav_REAL_phv_LAZYDEL_pbm_VALID_repl_EVAL : 1
+;
            unsigned long f_IVisUV_pav_REIFY_phv_HASKFLAGS_pfm_COMPILE
+D_pbm_TAIL_prv_WEAKREF : 1;
        } flagsraw;
    };
    union {                
    IV      svu_iv;    
    UV      svu_uv;    
    pMG*     svu_rv;    
    char*   svu_pv;    
    pMG**    svu_array;        
    HE**    svu_hash;        
    GP*    svu_gp;            
    }    sv_u;
};

#define SV pMG

[download]
Works on Visual C. Will generate millions of type warnings. Put right after the perl header includes. Makes debugging very easy. The SVANY is a MG struct. LVs are longer. SV type can't be an enum because enums must be 32 bits on MSVC (bad MS!!!).

In reply to Looking at a SV in C by bulk88

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