Use Linux-specific linker flags conditionally

[barracuda156]

This is not supported with macOS ld: https://github.com/InterLinked1/evergreen/blob/79e2da22a6620dbc59cca7019b07ff011c00d088/Makefile#L22C22-L22C38

[InterLinked1]

Thanks for reporting these issues - I only test on Linux distros and FreeBSD; if you have a solution that works with MacOS, we can include your fixes. However, I don't have a Mac so this isn't something I'd look into further myself.

[barracuda156]

Got it. I will try building it, if I get something working, I can make a PR.

[barracuda156]

It’s a bit more than a bunch of unsupported flags:

editor.c:318:21: error: implicit declaration of function 'memrchr' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                        const char *sp = memrchr(dst - FORMAT_FLOWED_WRAP_COL, ' ', FORMAT_FLOWED_WRAP_COL);
                                         ^
editor.c:318:21: note: did you mean 'memchr'?
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/string.h:70:7: note: 'memchr' declared here
void    *memchr(const void *__s, int __c, size_t __n);
         ^
editor.c:318:16: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Werror,-Wint-conversion]
                        const char *sp = memrchr(dst - FORMAT_FLOWED_WRAP_COL, ' ', FORMAT_FLOWED_WRAP_COL);
                                    ^    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
evergreen.c:68:10: fatal error: 'sys/eventfd.h' file not found
#include <sys/eventfd.h>
         ^~~~~~~~~~~~~~~
editor.c:865:15: error: implicit declaration of function 'memrchr' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                                last_sp = memrchr(s - outputcol, ' ', outputcol);
                                          ^
editor.c:865:13: error: incompatible integer to pointer conversion assigning to 'const char *' from 'int' [-Werror,-Wint-conversion]
                                last_sp = memrchr(s - outputcol, ' ', outputcol);
                                        ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 errors generated.
make: *** [editor.o] Error 1
1 error generated.
make: *** [evergreen.o] Error 1
smtp.c:218:4: error: implicit declaration of function 'explicit_bzero' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                        explicit_bzero(encoded, strlen(encoded));
                        ^
imap.c:146:29: error: 'format' attribute argument not supported: gnu_printf [-Werror,-Wignored-attributes]
static void __attribute__ ((format (gnu_printf, 7, 8))) log_mailimap(const char *file, int lineno, const char *func, int error, struct client *client, int code, const char *fmt, ...)
                            ^
imap.c:154:30: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
        vsnprintf(buf, sizeof(buf), fmt, ap);
                                    ^~~
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/secure/_stdio.h:75:63: note: expanded from macro 'vsnprintf'
  __builtin___vsnprintf_chk (str, len, 0, __darwin_obsz(str), format, ap)
                                                              ^~~~~~
imap.c:241:2: error: implicit declaration of function 'explicit_bzero' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        explicit_bzero(config->imap_password, sizeof(config->imap_password)); /* Zero the password out from memory */
        ^
1 error generated.
make: *** [smtp.o] Error 1
imap.c:958:91: error: incompatible pointer types passing 'struct client *' to parameter of type 'int (* _Nonnull)(void *, const void *, const void *)' [-Werror,-Wincompatible-pointer-types]
        qsort_r(mb_names, client->num_mailboxes, sizeof(struct mailbox_ref *), mailbox_name_cmp, client);
                                                                                                 ^~~~~~
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/stdlib.h:340:22: note: passing argument to parameter '__compar' here
            int (* _Nonnull __compar)(void *, const void *, const void *));
                            ^
4 errors generated.
make: *** [imap.o] Error 1

[InterLinked1]

It’s a bit more than a bunch of unsupported flags:

editor.c:318:21: error: implicit declaration of function 'memrchr' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                        const char *sp = memrchr(dst - FORMAT_FLOWED_WRAP_COL, ' ', FORMAT_FLOWED_WRAP_COL);
                                         ^
editor.c:318:21: note: did you mean 'memchr'?
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/string.h:70:7: note: 'memchr' declared here
void    *memchr(const void *__s, int __c, size_t __n);
         ^
editor.c:318:16: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Werror,-Wint-conversion]
                        const char *sp = memrchr(dst - FORMAT_FLOWED_WRAP_COL, ' ', FORMAT_FLOWED_WRAP_COL);
                                    ^    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
evergreen.c:68:10: fatal error: 'sys/eventfd.h' file not found
#include <sys/eventfd.h>
         ^~~~~~~~~~~~~~~
editor.c:865:15: error: implicit declaration of function 'memrchr' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                                last_sp = memrchr(s - outputcol, ' ', outputcol);
                                          ^
editor.c:865:13: error: incompatible integer to pointer conversion assigning to 'const char *' from 'int' [-Werror,-Wint-conversion]
                                last_sp = memrchr(s - outputcol, ' ', outputcol);
                                        ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 errors generated.
make: *** [editor.o] Error 1
1 error generated.
make: *** [evergreen.o] Error 1
smtp.c:218:4: error: implicit declaration of function 'explicit_bzero' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                        explicit_bzero(encoded, strlen(encoded));
                        ^
imap.c:146:29: error: 'format' attribute argument not supported: gnu_printf [-Werror,-Wignored-attributes]
static void __attribute__ ((format (gnu_printf, 7, 8))) log_mailimap(const char *file, int lineno, const char *func, int error, struct client *client, int code, const char *fmt, ...)
                            ^
imap.c:154:30: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
        vsnprintf(buf, sizeof(buf), fmt, ap);
                                    ^~~
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/secure/_stdio.h:75:63: note: expanded from macro 'vsnprintf'
  __builtin___vsnprintf_chk (str, len, 0, __darwin_obsz(str), format, ap)
                                                              ^~~~~~
imap.c:241:2: error: implicit declaration of function 'explicit_bzero' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        explicit_bzero(config->imap_password, sizeof(config->imap_password)); /* Zero the password out from memory */
        ^
1 error generated.
make: *** [smtp.o] Error 1
imap.c:958:91: error: incompatible pointer types passing 'struct client *' to parameter of type 'int (* _Nonnull)(void *, const void *, const void *)' [-Werror,-Wincompatible-pointer-types]
        qsort_r(mb_names, client->num_mailboxes, sizeof(struct mailbox_ref *), mailbox_name_cmp, client);
                                                                                                 ^~~~~~
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/stdlib.h:340:22: note: passing argument to parameter '__compar' here
            int (* _Nonnull __compar)(void *, const void *, const void *));
                            ^
4 errors generated.
make: *** [imap.o] Error 1

A few of these could probably be addressed easily (e.g. the format-nonliteral warning).

As far as memrchr, explicit_bzero, etc. not being available, wrappers may be needed for those. Looks like memrchr doesn't exist on MacOS: https://www.gnu.org/software/gnulib/manual/html_node/memrchr.html

[barracuda156]

For memrchr, will this work? https://github.com/macports/macports-ports/blob/43a40ec0d8e1c634af82d31d16097b26ed538d53/www/cgit/files/patch-add-memrchr.diff

explicit_bzero apparently can be emulated with memset_s or memzero, judging from patches in a few ports.

[InterLinked1]

For memrchr, will this work? https://github.com/macports/macports-ports/blob/43a40ec0d8e1c634af82d31d16097b26ed538d53/www/cgit/files/patch-add-memrchr.diff

Looks like it should... that seems like a reasonable approach and it looks GPL-compatible.

explicit_bzero apparently can be emulated with memset_s or memzero, judging from patches in a few ports.

Yeah, this one we need to be more careful with - memrchr is fairly trivial to write from scratch but zeroing memory can get optimized away by the compiler if we don't use the right function call. I think Gnulib has a version of it: https://www.gnu.org/software/gnulib/