编译bottledwater时avro-c检测失败及Makefile相关问题咨询

1. How does the shell expand PG_CONFIG in your Makefile? #

Let's break this down simply:

• Your Makefile first sets PG_CONFIG = pg_config — this creates a variable pointing to PostgreSQL's built-in configuration tool, pg_config.
• When the line PGXS := $(shell $(PG_CONFIG) --pgxs) runs, the shell does two key things:
  1. It resolves $(PG_CONFIG) to the actual pg_config executable by searching your system's PATH environment variable.
  2. It runs pg_config --pgxs directly in the shell, which outputs the full file path to PostgreSQL's pgxs makefile (this is a standard extension that handles all the build rules for PostgreSQL add-ons).
• The output of that command gets saved to the PGXS variable, and include $(PGXS) pulls in that makefile to use PostgreSQL's official extension build setup.

To see this in action yourself, just run pg_config --pgxs directly in your terminal — it will print the exact path the Makefile is using.

2. How to configure your setup so Bottledwater detects your avro-c directory? #

The error pops up because pkg-config can't find avro-c.pc — a metadata file it uses to locate libraries and headers. Since your compiled avro-c doesn't generate this file by default, here are three reliable fixes:

Option 1: Hardcode avro-c paths directly in the Makefile #

Skip pkg-config entirely by replacing the AVRO_CFLAGS and AVRO_LDFLAGS lines with your actual avro-c paths:

AVRO_CFLAGS = -I/home/jholmes/avro-c-1.8.2/build/avrolib/include
AVRO_LDFLAGS = -L/home/jholmes/avro-c-1.8.2/build/avrolib/lib -lavro

• -I tells the compiler where to find avro-c's header files
• -L tells the linker where to find avro-c's compiled libraries, and -lavro links against the avro library itself

Before running make, you may also need to set a temporary environment variable to ensure the linker can find the library at runtime:

export LD_LIBRARY_PATH=/home/jholmes/avro-c-1.8.2/build/avrolib/lib:$LD_LIBRARY_PATH

Option 2: Create a custom avro-c.pc file and point pkg-config to it #

1. First, make a pkgconfig directory inside your avro-c lib folder:

mkdir -p /home/jholmes/avro-c-1.8.2/build/avrolib/lib/pkgconfig

2. Create an avro-c.pc file in that directory with this content:

prefix=/home/jholmes/avro-c-1.8.2/build/avrolib
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: avro-c
Description: Apache Avro C library
Version: 1.8.2
Cflags: -I${includedir}
Libs: -L${libdir} -lavro

3. Tell pkg-config where to find this file by setting the PKG_CONFIG_PATH environment variable:

export PKG_CONFIG_PATH=/home/jholmes/avro-c-1.8.2/build/avrolib/lib/pkgconfig:$PKG_CONFIG_PATH

4. Now run make as usual — pkg-config should locate avro-c without issues.

Option 3: Recompile avro-c with installation support #

For a more permanent setup, recompile avro-c and install it to a dedicated path:

1. Navigate to your avro-c source directory:

cd /home/jholmes/avro-c-1.8.2

2. Run cmake with an installation prefix (adjust the path to your preference):

cmake -DCMAKE_INSTALL_PREFIX=/usr/local/avro-c-1.8.2 .

3. Compile and install:

make && sudo make install

This will generate an official avro-c.pc file in /usr/local/avro-c-1.8.2/lib/pkgconfig. Just add that directory to PKG_CONFIG_PATH before running make for Bottledwater.

内容的提问来源于stack exchange，提问作者MikiBelavista