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From: | Russell Shaw |
Subject: | Re: determine base type of a typedef |
Date: | Fri, 23 Oct 2020 12:09:46 +1100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
On 23/10/20 9:23 am, Anatoli wrote:
Hi All, Is there a way to determine with autoconf what's the base type of a typedef? I'm trying to accomplish the following: There are standard types time_t, off_t, size_t and similar that are defined differently on different platforms/OS. For example, time_t is defined as "long int" on Linux amd64, but as "long long int" on OpenBSD amd64. So when printing a time_t var with printf & co, on Linux it's OK to use "%ld" format specifier, but on OpenBSD it should be "%lld".
You could use an AC_COMPILE thing to run a small bit of C that does something like: int test(int argc, char **argv) { time_t t = -1; if(t < 0) { if(sizeof(time_t) == sizeof(int)) { printf("d"); } else if(sizeof(time_t) == sizeof(long int)) { printf("ld"); } else if(sizeof(time_t) == sizeof(long long int)) { printf("lld"); } else { printf("error"); } } else { if(sizeof(time_t) == sizeof(int)) { printf("u"); } else if(sizeof(time_t) == sizeof(long int)) { printf("lu"); } else if(sizeof(time_t) == sizeof(long long int)) { printf("llu"); } else { printf("error"); } } return 0; }
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