From d7f46cf28ea521eef0530a1a41af56a34dd89278 Mon Sep 17 00:00:00 2001
From: Pino Toscano <toscano.pino@tiscali.it>
Date: Tue, 30 Jul 2024 05:29:32 +0200
Subject: [PATCH 1/3] makefiles: recognize GNU/Hurd

Set HOST_HURD & HOST_UNIX for GNU/Hurd in the makefile-based build
system; the latter variable is important as it will include all the
commit Unix bits.
---
 mk/platform.mk | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mk/platform.mk b/mk/platform.mk
index fe960dedf..22c114a20 100644
--- a/mk/platform.mk
+++ b/mk/platform.mk
@@ -29,4 +29,8 @@ ifdef HOST_OS
     HOST_SOLARIS = 1
     HOST_UNIX = 1
   endif
+  ifeq ($(HOST_KERNEL), gnu)
+    HOST_HURD = 1
+    HOST_UNIX = 1
+  endif
 endif

From 7442f4a16143fe69a71949f1edbbbcab6862ed23 Mon Sep 17 00:00:00 2001
From: Pino Toscano <toscano.pino@tiscali.it>
Date: Tue, 30 Jul 2024 05:31:42 +0200
Subject: [PATCH 2/3] libutil: use /proc/self/exe on Hurd as well

Rely on the Linux-compatible procfs available on the Hurd to get the
path of the current executable.
---
 src/libutil/current-process.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libutil/current-process.cc b/src/libutil/current-process.cc
index c2b1ac500..0bc46d746 100644
--- a/src/libutil/current-process.cc
+++ b/src/libutil/current-process.cc
@@ -137,7 +137,7 @@ std::optional<Path> getSelfExe()
 {
     static auto cached = []() -> std::optional<Path>
     {
-        #if __linux__
+        #if __linux__ || __GNU__
         return readLink("/proc/self/exe");
         #elif __APPLE__
         char buf[1024];

From a1ccf6061396f398526bb99518cfd3b9c432aeb1 Mon Sep 17 00:00:00 2001
From: Pino Toscano <toscano.pino@tiscali.it>
Date: Tue, 30 Jul 2024 05:34:34 +0200
Subject: [PATCH 3/3] tests: define fallback PATH_MAX

Few filesystem-related tests rely on PATH_MAX for buffers, and PATH_MAX
is optional in POSIX (and not available on the Hurd). To make them build
and pass, provide a fallback definition of PATH_MAX in case not
available.

Ideally speaking, the tests ought to not unconditionally rely on
PATH_MAX, do alternative strategies (e.g. dynamically allocate buffers,
expand them as needed, etc); OTOH this is test code, so it would be more
work that what it would be worth, so IMHO the define fallback is good
enough.
---
 tests/unit/libutil/tests.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/unit/libutil/tests.cc b/tests/unit/libutil/tests.cc
index 8a3ca8561..2b73d323b 100644
--- a/tests/unit/libutil/tests.cc
+++ b/tests/unit/libutil/tests.cc
@@ -17,6 +17,10 @@
 # define FS_ROOT FS_SEP
 #endif
 
+#ifndef PATH_MAX
+# define PATH_MAX 4096
+#endif
+
 namespace nix {
 
 /* ----------- tests for util.hh ------------------------------------------------*/