[xmlsec] fix warning about ptr->func conversion

[Aleksey Sanin <aleksey src gnome org>]

commit ebbf6e958d8396160b0320d52f5ac8b24162a308
Author: Aleksey Sanin <aleksey aleksey com>
Date:   Sun May 9 14:07:26 2010 -0700

    fix warning about ptr->func conversion

 include/xmlsec/mscrypto/crypto.h |   16 +++++-----
 include/xmlsec/xmlsec.h          |   57 ++++++++++++++++++++++++++++++++++++++
 src/dl.c                         |   19 ++++++++++--
 src/openssl/app.c                |   42 +++++++++++++++++++++------
 4 files changed, 112 insertions(+), 22 deletions(-)
---
diff --git a/include/xmlsec/mscrypto/crypto.h b/include/xmlsec/mscrypto/crypto.h
index dd8a994..5f3142f 100644
--- a/include/xmlsec/mscrypto/crypto.h
+++ b/include/xmlsec/mscrypto/crypto.h
@@ -194,14 +194,14 @@ XMLSEC_CRYPTO_EXPORT xmlSecTransformId xmlSecMSCryptoTransformRsaSha512GetKlass(
         xmlSecMSCryptoTransformRsaPkcs1GetKlass()
 XMLSEC_CRYPTO_EXPORT xmlSecTransformId xmlSecMSCryptoTransformRsaPkcs1GetKlass(void);
 
-/**
- * xmlSecMSCryptoTransformRsaOaepId:
- *
- * The RSA OAEP key transport transform klass.
- */
-#define xmlSecMSCryptoTransformRsaOaepId \
-        xmlSecMSCryptoTransformRsaOaepGetKlass()
-XMLSEC_CRYPTO_EXPORT xmlSecTransformId xmlSecMSCryptoTransformRsaOaepGetKlass(void);
+/**
+ * xmlSecMSCryptoTransformRsaOaepId:
+ *
+ * The RSA OAEP key transport transform klass.
+ */
+#define xmlSecMSCryptoTransformRsaOaepId \
+        xmlSecMSCryptoTransformRsaOaepGetKlass()
+XMLSEC_CRYPTO_EXPORT xmlSecTransformId xmlSecMSCryptoTransformRsaOaepGetKlass(void);
 
 /**
  * xmlSecMSCryptoTransformRsaOaepId:
diff --git a/include/xmlsec/xmlsec.h b/include/xmlsec/xmlsec.h
index 9ab4cea..ad44918 100644
--- a/include/xmlsec/xmlsec.h
+++ b/include/xmlsec/xmlsec.h
@@ -150,6 +150,63 @@ XMLSEC_EXPORT int       xmlSecCheckVersionExt   (int major,
 #define ATTRIBUTE_UNUSED
 #endif
 
+/***********************************************************************
+ *
+ * Helpers to convert from void* to function pointer, this silence
+ * gcc warning
+ *
+ *     warning: ISO C forbids conversion of object pointer to function
+ *     pointer type
+ *
+ * The workaround is to declare a union that does the conversion. This is
+ * guaranteed (ISO/IEC 9899:1990 "C89"/"C90") to match exactly.
+ *
+ ***********************************************************************/
+
+/**
+ * XMLSEC_PTR_TO_FUNC_IMPL:
+ * @func_type:          the function type.
+ *
+ * Macro declares helper functions to convert between "void *" pointer and
+ * function pointer.
+ */
+#define XMLSEC_PTR_TO_FUNC_IMPL(func_type) \
+    union xmlSecPtrToFuncUnion_ ##func_type { \
+        void *ptr; \
+        func_type * func; \
+    } ; \
+    static func_type * xmlSecPtrToFunc_ ##func_type(void * ptr) { \
+         union xmlSecPtrToFuncUnion_ ##func_type x; \
+         x.ptr = ptr; \
+         return (x.func); \
+    } \
+    static void * xmlSecFuncToPtr_ ##func_type(func_type * func) { \
+         union xmlSecPtrToFuncUnion_ ##func_type x; \
+         x.func = func; \
+         return (x.ptr); \
+    }
+
+/**
+ * XMLSEC_PTR_TO_FUNC:
+ * @func_type:          the function type.
+ * @ptr:                the "void*" pointer to be converted.
+ *
+ * Macro converts from "void*" pointer to "func_type" function pointer.
+ */
+#define XMLSEC_PTR_TO_FUNC(func_type, ptr) \
+    xmlSecPtrToFunc_ ##func_type((ptr))
+
+/**
+ * XMLSEC_FUNC_TO_PTR:
+ * @func_type:          the function type.
+ * @func:               the "func_type" function pointer to be converted.
+ *
+ * Macro converts from "func_type" function pointer to "void*" pointer.
+ */
+#define XMLSEC_FUNC_TO_PTR(func_type, func) \
+    xmlSecFuncToPtr_ ##func_type((func))
+
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/src/dl.c b/src/dl.c
index 3771e84..d6f37ef 100644
--- a/src/dl.c
+++ b/src/dl.c
@@ -82,10 +82,14 @@ static int                      xmlSecCryptoDLLibrariesListFindByName   (xmlSecP
 
 typedef xmlSecCryptoDLFunctionsPtr (*xmlSecCryptoGetFunctionsCallback)(void);
 
+/* conversion from ptr to func "the right way" */
+XMLSEC_PTR_TO_FUNC_IMPL(xmlSecCryptoGetFunctionsCallback)
+
+
 static xmlSecCryptoDLLibraryPtr
 xmlSecCryptoDLLibraryCreate(const xmlChar* name) {
     xmlSecCryptoDLLibraryPtr lib;
-    xmlSecCryptoGetFunctionsCallback getFunctions;
+    xmlSecCryptoGetFunctionsCallback * getFunctions;
 
     xmlSecAssert2(name != NULL, NULL);
 
@@ -149,7 +153,9 @@ xmlSecCryptoDLLibraryCreate(const xmlChar* name) {
         return(NULL);
     }
 
-    getFunctions = (xmlSecCryptoGetFunctionsCallback)lt_dlsym(lib->handle, (char*)lib->getFunctionsName);
+    getFunctions = XMLSEC_PTR_TO_FUNC(xmlSecCryptoGetFunctionsCallback,
+                        lt_dlsym(lib->handle, (char*)lib->getFunctionsName)
+                    );
     if(getFunctions == NULL) {
         xmlSecError(XMLSEC_ERRORS_HERE,
                     "lt_dlsym",
@@ -175,7 +181,12 @@ xmlSecCryptoDLLibraryCreate(const xmlChar* name) {
         return(NULL);
     }
 
-    getFunctions = (xmlSecCryptoGetFunctionsCallback)GetProcAddress(lib->handle, (char*)lib->getFunctionsName);
+    getFunctions = XMLSEC_PTR_TO_FUNC(xmlSecCryptoGetFunctionsCallback,
+                        GetProcAddress(
+                            lib->handle,
+                            (const char*)lib->getFunctionsName
+                        )
+                    );
     if(getFunctions == NULL) {
         xmlSecError(XMLSEC_ERRORS_HERE,
                     "GetProcAddressA",
@@ -198,7 +209,7 @@ xmlSecCryptoDLLibraryCreate(const xmlChar* name) {
         return(NULL);
     }
 
-    lib->functions = getFunctions();
+    lib->functions = (*getFunctions)();
     if(lib->functions == NULL) {
         xmlSecError(XMLSEC_ERRORS_HERE,
                     "getFunctions",
diff --git a/src/openssl/app.c b/src/openssl/app.c
index fe427ea..1319b07 100644
--- a/src/openssl/app.c
+++ b/src/openssl/app.c
@@ -32,10 +32,20 @@
 #include <xmlsec/openssl/evp.h>
 #include <xmlsec/openssl/x509.h>
 
-static int              xmlSecOpenSSLAppLoadRANDFile            (const char *file);
-static int              xmlSecOpenSSLAppSaveRANDFile            (const char *file);
-static int              xmlSecOpenSSLDefaultPasswordCallback(char *buf, int bufsiz, int verify, void *userdata);
-static int      xmlSecOpenSSLDummyPasswordCallback  (char *buf, int bufsize, int verify, void *userdata);
+static int      xmlSecOpenSSLAppLoadRANDFile            (const char *file);
+static int      xmlSecOpenSSLAppSaveRANDFile            (const char *file);
+static int      xmlSecOpenSSLDefaultPasswordCallback    (char *buf,
+                                                         int bufsiz,
+                                                         int verify,
+                                                         void *userdata);
+static int      xmlSecOpenSSLDummyPasswordCallback      (char *buf,
+                                                         int bufsize,
+                                                         int verify,
+                                                         void *userdata);
+
+/* conversion from ptr to func "the right way" */
+XMLSEC_PTR_TO_FUNC_IMPL(pem_password_cb)
+
 
 /**
  * xmlSecOpenSSLAppInit:
@@ -234,13 +244,21 @@ xmlSecOpenSSLAppKeyLoadBIO(BIO* bio, xmlSecKeyDataFormat format,
     switch(format) {
     case xmlSecKeyDataFormatPem:
         /* try to read private key first */
+        if(pwd != NULL) {
             pKey = PEM_read_bio_PrivateKey(bio, NULL,
-            (pwd != NULL) ? xmlSecOpenSSLDummyPasswordCallback : (pem_password_cb*)pwdCallback,
-            (pwd != NULL) ? (void*)pwd : pwdCallbackCtx);
+                        xmlSecOpenSSLDummyPasswordCallback,
+                        (void*)pwd);
+        } else {
+            pKey = PEM_read_bio_PrivateKey(bio, NULL,
+                            XMLSEC_PTR_TO_FUNC(pem_password_cb, pwdCallback),
+                            pwdCallbackCtx);
+        }
         if(pKey == NULL) {
             /* go to start of the file and try to read public key */
             BIO_reset(bio);
-            pKey = PEM_read_bio_PUBKEY(bio, NULL, (pem_password_cb*)pwdCallback, pwdCallbackCtx);
+            pKey = PEM_read_bio_PUBKEY(bio, NULL,
+                            XMLSEC_PTR_TO_FUNC(pem_password_cb, pwdCallback),
+                            pwdCallbackCtx);
             if(pKey == NULL) {
                 xmlSecError(XMLSEC_ERRORS_HERE,
                             NULL,
@@ -270,7 +288,9 @@ xmlSecOpenSSLAppKeyLoadBIO(BIO* bio, xmlSecKeyDataFormat format,
         break;
     case xmlSecKeyDataFormatPkcs8Pem:
         /* try to read private key first */
-        pKey = PEM_read_bio_PrivateKey(bio, NULL, (pem_password_cb*)pwdCallback, pwdCallbackCtx);
+        pKey = PEM_read_bio_PrivateKey(bio, NULL,
+                            XMLSEC_PTR_TO_FUNC(pem_password_cb, pwdCallback),
+                            pwdCallbackCtx);
         if(pKey == NULL) {
             xmlSecError(XMLSEC_ERRORS_HERE,
                         NULL,
@@ -282,7 +302,9 @@ xmlSecOpenSSLAppKeyLoadBIO(BIO* bio, xmlSecKeyDataFormat format,
         break;
     case xmlSecKeyDataFormatPkcs8Der:
         /* try to read private key first */
-        pKey = d2i_PKCS8PrivateKey_bio(bio, NULL, (pem_password_cb*)pwdCallback, pwdCallbackCtx);
+        pKey = d2i_PKCS8PrivateKey_bio(bio, NULL,
+                            XMLSEC_PTR_TO_FUNC(pem_password_cb, pwdCallback),
+                            pwdCallbackCtx);
         if(pKey == NULL) {
             xmlSecError(XMLSEC_ERRORS_HERE,
                         NULL,
@@ -1513,7 +1535,7 @@ xmlSecOpenSSLAppSaveRANDFile(const char *file) {
  */
 void*
 xmlSecOpenSSLAppGetDefaultPwdCallback(void) {
-    return((void*)xmlSecOpenSSLDefaultPasswordCallback);
+    return XMLSEC_FUNC_TO_PTR(pem_password_cb, xmlSecOpenSSLDefaultPasswordCallback);
 }
 
 static int