Mary hinton commented on PROTON-57:
server_callback(pn_connector_t *ctor) -- char iresp[n];
-- char data[ctx->size + 16];
client_callback(pn_connector_t *ctor) -- char msg[ctx->size]
char data[ctx->size + 16];
pn_print_atoms(const pn_atoms_t * atoms) -- char buf[size]
pn_data_encode(pn_data_t *data, char *bytes, size_t size) -- pn_atom_t
atoms[data->size + data->extras];
pn_data_decode(pn_data_t *data, char *bytes, size_t size) -- pn_atom_t
pn_messenger_resolve(pn_messenger_t *messenger, char *address, char
**name) -- char domain[strlen(address) + 1];
pn_messenger_link(pn_messenger_t *messenger, const char *address, bool
sender) -- char copy[(address ? strlen(address) : 0) + 1];
pn_messenger_subscribe(pn_messenger_t *messenger, const char *source)
-- char copy[strlen(source) + 1];
outward_munge(pn_messenger_t *mng, pn_message_t *msg)
-- char buf[len + strlen(mng->name) + 4];
buf[strlen(mng->name) + 4];
pn_messenger_put(pn_messenger_t *messenger, pn_message_t *msg)
-- char encoded[size];
pn_sasl_plain(pn_sasl_t *sasl, const char *username, const char
*password) -- char iresp[size];
pn_fprint_data(FILE *stream, const char *bytes, size_t size)
-- char buf[capacity];
This list only includes the VLAs and doesn't include constant size arrays.
> Proton porting problems between current codebase and Visual Studio 2010
> Key: PROTON-57
> URL: https://issues.apache.org/jira/browse/PROTON-57
> Project: Qpid Proton
> Issue Type: Improvement
> Components: proton-c
> Environment: Windows using Visual Studio 2010
> Reporter: Mary hinton
> Labels: build
> This thread will be used to discuss the porting problems encountered using
> Visual Studio 2010
> Here’s the first one to discuss:
> 1. Visual Studio doesn’t support variable length arrays.
> a. Currently using malloc()/realloc() in my port just to get it to
> compile and be able to report memory allocation errors. This is not what I
> want to submit to the proton group for memory allocation.
> b. Cliff had a good method that included setting up macros and replace
> the VLAs with alloca() in the Windows version, but it could still cause
> problems when the stack overflowed. VLAs can also run out of stack space.
> c. _malloca() should be a better way than _alloca() on Visual Studio.
> Any messages under 1K would be allocated out of the stack. Over 1K will use
> heap. If the average messages are under 1K, this may be the most efficient
> way in Visual Studio. _malloca() also has new security enhancements.
> 1. Using _malloca() in the Windows version and VLA in Linux would
> require two macros. The major difference for the Linux version would be to
> use the new macro for VLA and to include the new free macro even though there
> is nothing to free using VLA. In Visual Studio, _freea(buf) will not free
> anything if it is allocating off the stack.
> Linux can continue to use VLAs.
> #ifdef C99
> #define PN_VLA(TYPE, buf, size) TYPE buf[size]
> #define PN_VLA_FREE
> #define PN_VLA(TYPE, buf, size) TYPE *buf = (TYPE*)
> #define PN_VLA_FREE(buf) _freea(buf)
> d. If the average size messages to allocate out of the stack needs to be
> increased for performance reasons, we can set up a new memory model. The 1K
> is not adjustable for _malloca().
> We can set up new macros along the lines of Microsoft’s suggestion below.
> “I would suggest something similar to what ATL does. Use alloca for small
> (where you define what that is) sizes and use heap allocation for larger
> ones. You can wrap the logic inside of a class or macros. To work around
> the fact that alloca isn't cleaned up at block scope, rewrite the block into
> functions or use lambdas. (I think alloca works inside of lambdas.)”
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