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Fix GCC-15, C23 compatibility and -Wincompatible-pointer-types errors

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A bug in gentoo linux https://bugs.gentoo.org/945183 reported that dnsmasq 2.90 fails to compile with GCC 15.

The issue is that while previous versions of GCC defaulted to the C17 standard and C23 could be selected with
"-std=c23" or "-std=gnu23", GCC 15 defaults to C23. In C23 incompatible pointer types are an error instead of
a warning, so the "int (*callback)()" incomplete prototypes cause errors.

For example, compiling dnsmasq 2.90 with gcc 14.2.1 and "-std=gnu23" fails with errors such as:
    lease.c: In function `lease_find_interfaces':
    lease.c:467:34: warning: passing argument 3 of `iface_enumerate' from incompatible pointer type [-Wincompatible-pointer-types[https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wincompatible-pointer-types]]
      467 |   iface_enumerate(AF_INET, &now, find_interface_v4);
          |                                  ^~~~~~~~~~~~~~~~~
          |                                  |
          |                                  int (*)(struct in_addr,  int,  char *, struct in_addr,  struct in_addr,  void *)
    In file included from lease.c:17:
    dnsmasq.h:1662:50: note: expected `int (*)(void)' but argument is of type `int (*)(struct in_addr,  int,  char *, struct in_addr,  struct in_addr,  void *)'
     1662 | int iface_enumerate(int family, void *parm, int (callback)());
          |                                             ~~~~~^~~~~~~~~~~

This patch uses a typedef'ed union of pointer types to get type checking of the pointers. If that's too complicated,
another way might be to use (void *) casts to disable type checking.

Also, some of the IPv6 callbacks had "int preferred, int valid" and some had
"unsigned int preferred, unsigned int valid". This patch changes them all to "unsigned int"
so they're the same and to avoid casting "u32" to "int", eg:
    u32 preferred = 0xffffffff;
    callback(..., (int)preferred, ...)
Even if those cast values aren't used in the callback, casting u32 to "int" feels bad, especially if "int" is 32 bits.
This commit is contained in:
gen2dev
2024-12-01 22:53:16 +00:00
committed by Simon Kelley
parent a8088e331a
commit da2cc84854
9 changed files with 40 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
src/radv.c
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@@ -58,7 +58,7 @@ static int add_prefixes(struct in6_addr *local, int prefix,
unsigned int preferred, unsigned int valid, void *vparam);
static int iface_search(struct in6_addr *local, int prefix,
int scope, int if_index, int flags,
int prefered, int valid, void *vparam);
unsigned int prefered, unsigned int valid, void *vparam);
static int add_lla(int index, unsigned int type, char *mac, size_t maclen, void *parm);
static void new_timeout(struct dhcp_context *context, char *iface_name, time_t now);
static unsigned int calc_lifetime(struct ra_interface *ra);
@@ -307,7 +307,7 @@ static void send_ra_alias(time_t now, int iface, char *iface_name, struct in6_ad
/* If no link-local address then we can't advertise since source address of
advertisement must be link local address: RFC 4861 para 6.1.2. */
if (!iface_enumerate(AF_INET6, &parm, add_prefixes) ||
if (!iface_enumerate(AF_INET6, &parm, (callback_t){.af_inet6=add_prefixes}) ||
parm.link_pref_time == 0)
return;
@@ -449,7 +449,7 @@ static void send_ra_alias(time_t now, int iface, char *iface_name, struct in6_ad
put_opt6_long(mtu);
}
iface_enumerate(AF_LOCAL, &send_iface, add_lla);
iface_enumerate(AF_LOCAL, &send_iface, (callback_t){.af_local=add_lla});
/* RDNSS, RFC 6106, use relevant DHCP6 options */
(void)option_filter(parm.tags, NULL, daemon->dhcp_opts6);
@@ -823,7 +823,7 @@ time_t periodic_ra(time_t now)
param.iface = context->if_index;
new_timeout(context, param.name, now);
}
else if (iface_enumerate(AF_INET6, &param, iface_search))
else if (iface_enumerate(AF_INET6, &param, (callback_t){.af_inet6=iface_search}))
/* There's a context overdue, but we can't find an interface
associated with it, because it's for a subnet we dont
have an interface on. Probably we're doing DHCP on
@@ -856,7 +856,7 @@ time_t periodic_ra(time_t now)
aparam.iface = param.iface;
aparam.alias_ifs = NULL;
aparam.num_alias_ifs = 0;
iface_enumerate(AF_LOCAL, &aparam, send_ra_to_aliases);
iface_enumerate(AF_LOCAL, &aparam, (callback_t){.af_local=send_ra_to_aliases});
my_syslog(MS_DHCP | LOG_INFO, "RTR-ADVERT(%s) %s => %d alias(es)",
param.name, daemon->addrbuff, aparam.num_alias_ifs);
@@ -871,7 +871,7 @@ time_t periodic_ra(time_t now)
those. */
aparam.max_alias_ifs = aparam.num_alias_ifs;
aparam.num_alias_ifs = 0;
iface_enumerate(AF_LOCAL, &aparam, send_ra_to_aliases);
iface_enumerate(AF_LOCAL, &aparam, (callback_t){.af_local=send_ra_to_aliases});
for (; aparam.num_alias_ifs; aparam.num_alias_ifs--)
{
my_syslog(MS_DHCP | LOG_INFO, "RTR-ADVERT(%s) %s => i/f %d",
@@ -920,7 +920,7 @@ static int send_ra_to_aliases(int index, unsigned int type, char *mac, size_t ma
static int iface_search(struct in6_addr *local, int prefix,
int scope, int if_index, int flags,
int preferred, int valid, void *vparam)
unsigned int preferred, unsigned int valid, void *vparam)
{
struct search_param *param = vparam;
struct dhcp_context *context;