[openwrt/openwrt] tools/gnulib: allow forced exclusion of functions after configure

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/efdd65cb871c1fe369a56351064aca363fd792af

commit efdd65cb871c1fe369a56351064aca363fd792af
Author: Michael Pratt <mcpratt at pm.me>
AuthorDate: Fri Jun 7 23:52:56 2024 -0400

    tools/gnulib: allow forced exclusion of functions after configure
    
    Overriding variables used in both the macros and the headers
    like setting REPLACE_FCNTL to 0 while invoking Make causes the
    function aliases like rpl_fcntl() to not be defined,
    however the object may still be built with the fnctl() function.
    
    Usually this is enough for building while avoiding
    the need to link the resulting libgnu library
    to every single other build target for a project
    in order to include the gnulib copy of the function,
    because in these cases we don't care which version
    of the function is used.
    
    However for functions like fcntl() this doesn't work
    as it is designed to use either the alias or standard declaration
    from gnulib headers in order to be
    a wrapper for the native host copy of fcntl()
    by containing recursive calls to fcntl() within itself
    after undefining the gnulib function declaration.
    
    Overriding the variables used by the header when invoking Make
    causes the header's declarations to be blocked,
    and this results in the gnulib version of fcntl()
    to call itself recursively and indefinitely
    leading to segmentation faults.
    
    Fix this by using macros defined with those variables
    in order to exclude the function during preprocessing.
    
    While at it, do the same for reallocarray()
    so that the configure option --avoid=reallocarray
    and Make variable REPLACE_REALLOCARRAY set to 0
    would have a similar effect.
    
    In the future this patch can be expanded to include
    more functions and some version of this may be upstreamable.
    
    Signed-off-by: Michael Pratt <mcpratt at pm.me>
    Link: https://github.com/openwrt/openwrt/pull/15690
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 .../200-force-disable-after-configure.patch        | 56 ++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/tools/gnulib/patches/200-force-disable-after-configure.patch b/tools/gnulib/patches/200-force-disable-after-configure.patch
new file mode 100644
index 0000000000..55335b27d2
--- /dev/null
+++ b/tools/gnulib/patches/200-force-disable-after-configure.patch
@@ -0,0 +1,56 @@
+--- a/lib/fcntl.c
++++ b/lib/fcntl.c
+@@ -198,6 +198,8 @@ static int klibc_fcntl (int fd, int acti
+    FD_CLOEXEC is portable, but other flags may be present); otherwise
+    return -1 and set errno.  */
+ 
++#if (GNULIB_defined_fcntl || GNULIB_defined_rpl_fcntl)
++
+ int
+ fcntl (int fd, int action, /* arg */...)
+ #undef fcntl
+@@ -443,6 +445,8 @@ fcntl (int fd, int action, /* arg */...)
+   return result;
+ }
+ 
++#endif /* (GNULIB_defined_fcntl || GNULIB_defined_rpl_fcntl) */
++
+ static int
+ rpl_fcntl_DUPFD (int fd, int target)
+ {
+--- a/lib/stdlib.in.h
++++ b/lib/stdlib.in.h
+@@ -1447,10 +1447,16 @@ _GL_FUNCDECL_RPL (reallocarray, void *,
+                   (void *ptr, size_t nmemb, size_t size));
+ _GL_CXXALIAS_RPL (reallocarray, void *,
+                   (void *ptr, size_t nmemb, size_t size));
++#  if !GNULIB_defined_rpl_reallocarray
++#   define GNULIB_defined_rpl_reallocarray 1
++#  endif
+ # else
+ #  if ! @HAVE_REALLOCARRAY@
+ _GL_FUNCDECL_SYS (reallocarray, void *,
+                   (void *ptr, size_t nmemb, size_t size));
++#   if !GNULIB_defined_reallocarray
++#    define GNULIB_defined_reallocarray 1
++#   endif
+ #  endif
+ _GL_CXXALIAS_SYS (reallocarray, void *,
+                   (void *ptr, size_t nmemb, size_t size));
+--- a/lib/reallocarray.c
++++ b/lib/reallocarray.c
+@@ -23,6 +23,8 @@
+ #include <stdlib.h>
+ #include <errno.h>
+ 
++#if (GNULIB_defined_reallocarray || GNULIB_defined_rpl_reallocarray)
++
+ void *
+ reallocarray (void *ptr, size_t nmemb, size_t size)
+ {
+@@ -36,3 +38,5 @@ reallocarray (void *ptr, size_t nmemb, s
+   /* Rely on the semantics of GNU realloc.  */
+   return realloc (ptr, nbytes);
+ }
++
++#endif /* (GNULIB_defined_reallocarray || GNULIB_defined_rpl_reallocarray) */