/* Part of SWI-Prolog Author: Keri Harris and Jan Wielemaker E-mail: keri@gentoo.org WWW: http://www.swi-prolog.org Copyright (c) 2018, VU University Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #define __assert_fail __sys_assert_fail #include #include #include /* we can use this on systems that have no modular heap */ /* TBD: On windows we really must call PL_free() or use */ /* the global heap somehow */ #define PL_free(ptr) free(ptr) /* redefine assert(), such that we can pick up the result in Prolog instead of crashing. */ static struct assert_data { const char *assertion; const char *file; unsigned int line; const char *function; int failed; } assert_failure; void __my_assert_fail(const char *assertion, const char *file, unsigned int line, const char *function) { assert_failure.assertion = assertion; assert_failure.file = file; assert_failure.line = line; assert_failure.function = function; assert_failure.failed = 1; } #undef __assert_fail #define __assert_fail __my_assert_fail struct assert_data * get_assertion(void) { if ( assert_failure.failed ) { assert_failure.failed = 0; return &assert_failure; } return NULL; } /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Parameter direction Along with being able to understand the type of a parameter, a marshaller naturally needs to understand the direction (input/output) of a parameter: 1. return parameters. (Prolog output) 2. 'in' parameters. (Prolog inputs) 3. 'out' parameters. (Prolog outputs) 4. 'in-out' parameters. (A Prolog input+output mapped to a single function parameter) (return parameters are typically just a special case of an 'out' parameter). Some example functions covering these cases follow: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ /* return value */ int test_int_return(void) { return 42; } /* in parameter */ void test_int_in(int v) { assert(v == 42); } /* out parameter */ void test_int_out(int *v) { *v = 42; } /* in-out parameter */ void test_int_in_out(int *v) { assert(*v == 42); *v = 24; } /* Special handling may be required to handle the special case where a pointer type can be NULL. For example: */ /* return value; NULL */ char* test_null_return(void) { return NULL; } /* in parameter; NULL */ void test_null_in(char *v) { assert(v == NULL); } /* out parameter; NULL */ void test_null_out(char **v) { *v = NULL; } /* in-out parameter; NULL */ void test_null_in_out(char **v) { assert(*v == NULL); *v = NULL; } /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * memory management A marshaller should be able to track who "owns" a parameter and is thus responsible for eventually freeing resources associated with that parameter. When a parameter passes between Prolog <-> C, there are three types of transfer-of-ownership: 1. no transfer of ownership * 'in' parameters must be freed from Prolog * 'out' parameters must not be freed from Prolog * the 'in' component of 'in-out' parameters must be freed from Prolog 2. full transfer of ownership * 'in' parameters must not be freed from Prolog * 'out' parameters must be freed from Prolog * the 'out' component of 'in-out' parameters must be freed from Prolog 3. only transfer ownership of the container of a complex parameter (array, struct etc) * the member elements of 'in' parameters must be freed from Prolog * the container (but not the member elements) of 'out' parameters must be freed from Prolog * the member elements of the 'in' component, and the container (but not the member elements) of the 'out' component, of 'in-out' parameters must be freed from Prolog (As mentioned earlier, parameters/member-elements are freed from Prolog either via AGC or with explicit calls to c_free/1). Some example functions covering these cases follow: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ /* in parameter; do not transfer ownership */ void test_transfer_none_in(char *v) { assert(strcmp("foo", v)==0); } /* in parameter; full transfer of ownership */ void test_transfer_full_in(char *v) { assert(strcmp("foo", v)==0); PL_free(v); } /* out parameter; do not transfer ownership */ void test_transfer_none_out(char **v) { *v = "foo"; } /* out parameter; full transfer of ownership */ void test_transfer_full_out(char **v) { *v = strdup("foo"); } /* in-out parameter; do not transfer ownership */ void test_transfer_none_in_out(char **v) { assert(strcmp("foo", *v)==0); *v = "bar"; } /* in-out parameter; full transfer of ownership */ void test_transfer_full_in_out(char **v) { assert(strcmp("foo", *v)==0); PL_free(*v); *v = strdup("bar"); } /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Container types (e.g. arrays or structs) can be a bit more complicated to deal with as the parameter may have a different ownership than the elements/field-values that make up the parameter. For example: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ /* in parameter; do not transfer ownership */ void tests_array_transfer_none_in (char **array) { assert(strcmp("foo", array[0])==0); assert(strcmp("bar", array[1])==0); } /* in parameter; full transfer of ownership */ void tests_array_transfer_full_in (char **array) { assert(strcmp("foo", array[0])==0); assert(strcmp("bar", array[1])==0); PL_free(array[0]); PL_free(array[1]); PL_free(array); } /* in parameter; transfer container of array */ void test_array_transfer_container_in(char **array) { assert(strcmp("foo", array[0])==0); assert(strcmp("bar", array[1])==0); PL_free(array); } /* out parameter; do not transfer ownership */ void test_array_transfer_none_out(char ***array) { static char *array_[] = { "foo", "bar" }; *array = array_; } /* out parameter; full transfer of ownership */ void test_array_transfer_full_out(char ***array) { *array = malloc(2 * sizeof(char*)); (*array)[0] = strdup("foo"); (*array)[1] = strdup("bar"); } /* out parameter; transfer container of array */ void test_array_transfer_container_out(char ***array) { *array = malloc(2 * sizeof(char*)); (*array)[0] = "foo"; (*array)[1] = "bar"; } /* in-out parameter; do not transfer ownership */ void test_array_transfer_none_in_out(char ***array) { static char *array_[] = { "FOO", "BAR" }; assert(strcmp("foo", (*array)[0])==0); assert(strcmp("bar", (*array)[1])==0); *array = array_; } /* in-out parameter; full transfer of ownership */ void test_array_transfer_full_in_out(char ***array) { assert(strcmp("foo", (*array)[0])==0); assert(strcmp("bar", (*array)[1])==0); PL_free((*array)[0]); PL_free((*array)[1]); PL_free(*array); *array = malloc(2 * sizeof(char*)); (*array)[0] = strdup("FOO"); (*array)[1] = strdup("BAR"); } /* in-out parameter; transfer container of array */ void test_array_transfer_container_in_out(char ***array) { assert(strcmp("foo", (*array)[0])==0); assert(strcmp("bar", (*array)[1])==0); PL_free(*array); *array = malloc(2 * sizeof(char*)); (*array)[0] = "FOO"; (*array)[1] = "BAR"; } /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A marshaller should (ideally) also be able to handle the case where a C function is 'broken' and does not allocate an out parameter that is described as having full transfer of ownership. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ /* out parameter; full transfer of ownership */ void test_transfer_dangling_out(char **v) { } /******************************* * FREE * *******************************/ /* On Windows we cannot use free from libc as we need to call from the same module */ void myfree(void *ptr) { free(ptr); }