The gcc compiler issues the following warnings.

[batmanovnn]

The gcc compiler issues the following warnings:

tzdump.c: In function 'dumptzdata':
tzdump.c:486:37: warning: format '%d' expects argument of type 'int', but argument 3 has type 'long int' [-Wformat=]
    (void)printf("transit[%d]: time=%d (%s) type=%d\n",
                                    ~^
                                    %ld
     i, transit[i].time, ctimeGMT(transit[i].time),
        ~~~~~~~~~~~~~~~               
tzdump.c:486:50: warning: format '%d' expects argument of type 'int', but argument 5 has type 'long int' [-Wformat=]
    (void)printf("transit[%d]: time=%d (%s) type=%d\n",
                                                 ~^
                                                 %ld
tzdump.c:488:5:
     transit[i].type);
     ~~~~~~~~~~~~~~~                               
tzdump.c:503:9: warning: implicit declaration of function 'isprint' [-Wimplicit-function-declaration]
    if ( isprint(chars[i]) )
         ^~~~~~~
tzdump.c:518:38: warning: format '%d' expects argument of type 'int', but argument 3 has type 'time_t {aka long int}' [-Wformat=]
    (void)printf("leaps[%d]: transit=%d correct=%d\n",
                                     ~^
                                     %ld
      i, leaps[i].transit, leaps[i].correct);
         ~~~~~~~~~~~~~~~~              
tzdump.c:518:49: warning: format '%d' expects argument of type 'int', but argument 4 has type 'long int' [-Wformat=]
    (void)printf("leaps[%d]: transit=%d correct=%d\n",
                                                ~^
                                                %ld
      i, leaps[i].transit, leaps[i].correct);
                           ~~~~~~~~~~~~~~~~       
tzdump.c:626:30: warning: format '%d' expects argument of type 'int', but argument 2 has type 'time_t {aka long int}' [-Wformat=]
   (void)printf("tt[0]: time=%d (%s) index=%d type=%d\n",
                             ~^
                             %ld
     tt[0].time, ctimeGMT(tt[0].time),
     ~~~~~~~~~~                
tzdump.c:629:30: warning: format '%d' expects argument of type 'int', but argument 2 has type 'time_t {aka long int}' [-Wformat=]
   (void)printf("tt[1]: time=%d (%s) index=%d type=%d\n",
                             ~^
                             %ld
     tt[1].time, ctimeGMT(tt[1].time),
     ~~~~~~~~~~  

Version compiler:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/7/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 7.4.0-1ubuntu1_18.04.1' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr --with-gcc-major-version-only --program-suffix=-7 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)

[kurahaupo]

Note that time_t will correspond to different int sizes on different hosts.

When printing (or converting) an integer of unknown size, the portable solution is to cast the value to (intmax_t) or (uintmax_t), and use %jd or %ju in the format string.

(I would recommend using #include <stdint.h> both for this, and to convert most declaration types to standard types for explicit sizes, such as uint8_t & uint32_t.)