Merge #11984: doc: Update OpenBSD build instructions for 6.2 (cont'd)

6915f93 doc: Update OpenBSD build instructions for 6.2 (Wladimir J. van der Laan)

Pull request description:

  (this continues #11442)
  There is no more need to install a new compiler. This simplifies instructions a lot.

  From discussion with @fanquake on IRC I first wanted to add a new section for 6.2, but that made the document a complex mess. I think it's good enough (and more maintainable too) to only support the most recent release.

  Includes #11976.

  I moved the "resource limits" section to the end as I didn't seem to need it with clang, but this may vary based on source changes and the phase of the moon so it's good to keep it as optional extra information.

Tree-SHA512: 15794afec6d682323d0aa13c7616d009acb7fce8b0ef5d2106261f2ebd86b7b2fe66040c04860d9bf2f0c1934fbdc2b594b8c09a98accfaac04f3daf9a6cadf3

doc/build-openbsd.md

@@ -23,47 +23,31 @@ git clone https://github.com/bitcoin/bitcoin.git
 
 See [dependencies.md](dependencies.md) for a complete overview.
 
-GCC
--------
-
-The default C++ compiler that comes with OpenBSD 6.2 is g++ 4.2.1. This version is old (from 2007), and is not able to compile the current version of Bitcoin Core because it has no C++11 support. We'll install a newer version of GCC:
-
-```bash
- pkg_add g++
- ```
-
- This compiler will not overwrite the system compiler, it will be installed as `egcc` and `eg++` in `/usr/local/bin`.
+**Important**: From OpenBSD 6.2 onwards a C++11-supporting clang compiler is
+part of the base image, and while building it is necessary to make sure that this
+compiler is used and not ancient g++ 4.2.1. This is done by appending
+`CC=cc CXX=c++` to configuration commands. Mixing different compilers
+within the same executable will result in linker errors.
 
 ### Building BerkeleyDB
 
-BerkeleyDB is only necessary for the wallet functionality. To skip this, pass `--disable-wallet` to `./configure`.
+BerkeleyDB is only necessary for the wallet functionality. To skip this, pass
+`--disable-wallet` to `./configure` and skip to the next section.
 
 It is recommended to use Berkeley DB 4.8. You cannot use the BerkeleyDB library
 from ports, for the same reason as boost above (g++/libstd++ incompatibility).
 If you have to build it yourself, you can use [the installation script included
-in contrib/](contrib/install_db4.sh) like so
+in contrib/](/contrib/install_db4.sh) like so
 
 ```shell
-./contrib/install_db4.sh `pwd` CC=egcc CXX=eg++ CPP=ecpp
+./contrib/install_db4.sh `pwd` CC=cc CXX=c++
 ```
 
-from the root of the repository.
-
-### Resource limits
-
-The standard ulimit restrictions in OpenBSD are very strict:
-
-    data(kbytes)         1572864
-
-This, unfortunately, may no longer be enough to compile some `.cpp` files in the project,
-at least with GCC 4.9.4 (see issue [#6658](https://github.com/bitcoin/bitcoin/issues/6658)).
-If your user is in the `staff` group the limit can be raised with:
-
-    ulimit -d 3000000
+from the root of the repository. Then set `BDB_PREFIX` for the next section:
 
-The change will only affect the current shell and processes spawned by it. To
-make the change system-wide, change `datasize-cur` and `datasize-max` in
-`/etc/login.conf`, and reboot.
+```shell
+export BDB_PREFIX="$PWD/db4"
+```
 
 ### Building Bitcoin Core
 
@@ -79,13 +63,13 @@ Make sure `BDB_PREFIX` is set to the appropriate path from the above steps.
 
 To configure with wallet:
 ```bash
-./configure --with-gui=no CC=egcc CXX=eg++ CPP=ecpp \
+./configure --with-gui=no CC=cc CXX=c++ \
     BDB_LIBS="-L${BDB_PREFIX}/lib -ldb_cxx-4.8" BDB_CFLAGS="-I${BDB_PREFIX}/include"
 ```
 
 To configure without wallet:
 ```bash
-./configure --disable-wallet --with-gui=no CC=egcc CXX=eg++ CPP=ecpp
+./configure --disable-wallet --with-gui=no CC=cc CXX=c++
 ```
 
 Build and run the tests:
@@ -94,13 +78,23 @@ gmake # use -jX here for parallelism
 gmake check
 ```
 
-Clang
-------------------------------
+Resource limits
+-------------------
 
-```bash
-pkg_add llvm
+If the build runs into out-of-memory errors, the instructions in this section
+might help.
+
+The standard ulimit restrictions in OpenBSD are very strict:
+
+    data(kbytes)         1572864
+
+This, unfortunately, in some cases not enough to compile some `.cpp` files in the project,
+(see issue [#6658](https://github.com/bitcoin/bitcoin/issues/6658)).
+If your user is in the `staff` group the limit can be raised with:
+
+    ulimit -d 3000000
+
+The change will only affect the current shell and processes spawned by it. To
+make the change system-wide, change `datasize-cur` and `datasize-max` in
+`/etc/login.conf`, and reboot.
 
-./configure --disable-wallet --with-gui=no CC=clang CXX=clang++
-gmake # use -jX here for parallelism
-gmake check
-```