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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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21
src/libutil-c/nix_api_util.cc
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@ -64,7 +64,11 @@ const char * nix_version_get()
// Implementations
nix_err nix_setting_get(nix_c_context * context, const char * key, void * callback, void * user_data)
nix_err nix_setting_get(
nix_c_context * context,
const char * key,
void (*callback)(const char * start, unsigned int n, void * user_data),
void * user_data)
{
if (context)
context->last_err_code = NIX_OK;
@ -115,7 +119,11 @@ const char * nix_err_msg(nix_c_context * context, const nix_c_context * read_con
return nullptr;
}
nix_err nix_err_name(nix_c_context * context, const nix_c_context * read_context, void * callback, void * user_data)
nix_err nix_err_name(
nix_c_context * context,
const nix_c_context * read_context,
void (*callback)(const char * start, unsigned int n, void * user_data),
void * user_data)
{
if (context)
context->last_err_code = NIX_OK;
@ -125,7 +133,11 @@ nix_err nix_err_name(nix_c_context * context, const nix_c_context * read_context
return call_nix_get_string_callback(read_context->name, callback, user_data);
}
nix_err nix_err_info_msg(nix_c_context * context, const nix_c_context * read_context, void * callback, void * user_data)
nix_err nix_err_info_msg(
nix_c_context * context,
const nix_c_context * read_context,
void (*callback)(const char * start, unsigned int n, void * user_data),
void * user_data)
{
if (context)
context->last_err_code = NIX_OK;
@ -141,7 +153,8 @@ nix_err nix_err_code(const nix_c_context * read_context)
}
// internal
nix_err call_nix_get_string_callback(const std::string str, void * callback, void * user_data)
nix_err call_nix_get_string_callback(
const std::string str, void (*callback)(const char * start, unsigned int n, void * user_data), void * user_data)
{
((nix_get_string_callback) callback)(str.c_str(), str.size(), user_data);
return NIX_OK;