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C API: Safer function pointer casting

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See https://github.com/NixOS/nix/pull/8699#discussion_r1554312181

Casting a function pointer to `void*` is undefined behavior in the C
spec, since there are platforms with different sizes for these two kinds
of pointers. A safe alternative might be `void (*callback)()`
This commit is contained in:
José Luis Lafuente 2024-04-12 21:41:15 +02:00
parent 5b9cb8b372
commit 01bad63c72
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GPG key ID: 8A3455EBE455489A
8 changed files with 79 additions and 29 deletions
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3
tests/unit/libutil-support/tests/string_callback.cc
View file

@ -2,7 +2,8 @@
namespace nix::testing {
void observe_string_cb(const char * start, unsigned int n, std::string * user_data) {
void observe_string_cb(const char * start, unsigned int n, std::string * user_data)
{
*user_data = std::string(start);
}

9
tests/unit/libutil-support/tests/string_callback.hh
View file

@ -4,9 +4,14 @@
namespace nix::testing {
void observe_string_cb(const char * start, unsigned int n, std::string * user_data);
inline void * observe_string_cb_data(std::string & out) {
inline void * observe_string_cb_data(std::string & out)
{
return (void *) &out;
};
#define OBSERVE_STRING(str) (void *)nix::testing::observe_string_cb, nix::testing::observe_string_cb_data(str)
#define OBSERVE_STRING(str) \
(void (*)(const char *, unsigned int, void *)) nix::testing::observe_string_cb, \
nix::testing::observe_string_cb_data(str)
}