From b3b621b17c62ee36c5a391a65e9c8a308e1885aa Mon Sep 17 00:00:00 2001
From: "David E. Wheeler" <david@justatheory.com>
Date: Fri, 12 Sep 2025 16:45:22 -0400
Subject: [PATCH] Fix compile error on macOS

I was getting this error on macOS:

```
ld: library 'c++' not found
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
```

Took a while to track down the issue, but it turned out this warning at
the end of `cmake` was key:

```
CMake Warning at src/CMakeLists.txt:40 (target_link_libraries):
  Target "clickhouse_fdw" requests linking to directory
  "/Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk".  Targets may link
  only to libraries.  CMake is dropping the item.
```

This is fine, except that that CMake doesn't remove the option this
directory points to. The option is stored by `pg_config`; you can see it
here:

``` console
pg_config --ldflags
-isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX15.5.sdk -L/opt/homebrew/opt/readline/lib -Wl,-dead_strip_dylibs
```

What we need to do is remove both the macOS SDK and `-isysroot`. So add
a section to `CMakeLists.txt` that uses `REGEX REPLACE` to remove the
complete option from the output of `pg_config` on macOS.
---
 CMakeLists.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 73a7714..66344fb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -44,6 +44,10 @@ exec_program(${PG_CONFIG} ARGS --bindir OUTPUT_VARIABLE PGSQL_BINDIR)
 exec_program(${PG_CONFIG} ARGS --cppflags OUTPUT_VARIABLE PGSQL_CPPFLAGS)
 exec_program(${PG_CONFIG} ARGS --ldflags OUTPUT_VARIABLE PGSQL_LDFLAGS)
 exec_program(${PG_CONFIG} ARGS --libs OUTPUT_VARIABLE PGSQL_LIBS)
+if(APPLE)
+string(REGEX REPLACE "-isysroot[ ]+[^ ]+ " "" PGSQL_LDFLAGS ${PGSQL_LDFLAGS})
+string(REGEX REPLACE "-isysroot[ ]+[^ ]+ " "" PGSQL_CPPFLAGS ${PGSQL_CPPFLAGS})
+endif(APPLE)
 
 #------------------------------------------------------------------------------
 # tests