new doc

Author: digoal

201509/20150907_03.md

@@ -0,0 +1,91 @@
+## PostgreSQL src/Makefile.global中的小坑   
+                                                                   
+### 作者                                                                   
+digoal                                                                   
+                                                                   
+### 日期                                                                   
+2015-09-07                                                                 
+                                                                   
+### 标签                                                                   
+PostgreSQL , 编译 , makefile              
+                                                                   
+----                                                                   
+                                                                   
+## 背景       
+在编译一个插件时发现PostgreSQL的src/Makefile.global可能有一些坑你会踩到，  
+  
+我们来看看坑是什么？  
+  
+src/Makefile.global  
+  
+```  
+datadir := ${datarootdir}  
+ifeq "$(findstring pgsql, $(datadir))" ""  
+ifeq "$(findstring postgres, $(datadir))" ""  
+override datadir := $(datadir)/postgresql  
+endif  
+endif  
+  
+sysconfdir := ${prefix}/etc  
+ifeq "$(findstring pgsql, $(sysconfdir))" ""  
+ifeq "$(findstring postgres, $(sysconfdir))" ""  
+override sysconfdir := $(sysconfdir)/postgresql  
+endif  
+endif  
+  
+libdir := ${exec_prefix}/lib  
+  
+pkglibdir = $(libdir)  
+ifeq "$(findstring pgsql, $(pkglibdir))" ""  
+ifeq "$(findstring postgres, $(pkglibdir))" ""  
+override pkglibdir := $(pkglibdir)/postgresql  
+endif  
+endif  
+  
+includedir := ${prefix}/include  
+  
+pkgincludedir = $(includedir)  
+ifeq "$(findstring pgsql, $(pkgincludedir))" ""  
+ifeq "$(findstring postgres, $(pkgincludedir))" ""  
+override pkgincludedir := $(pkgincludedir)/postgresql  
+endif  
+endif  
+  
+mandir := ${datarootdir}/man  
+  
+docdir := ${datarootdir}/doc/${PACKAGE_TARNAME}  
+ifeq "$(findstring pgsql, $(docdir))" ""  
+ifeq "$(findstring postgres, $(docdir))" ""  
+override docdir := $(docdir)/postgresql  
+endif  
+endif  
+```  
+  
+注意，当这些目录中没有出现pgsql, postgres时，自动会在原有目录下新增一个postgresql目录。  
+  
+这点可能酿成大错，例如你的环境变量，或者代码中有这种强依赖的话，在更换主目录后就可能出现问题。  
+  
+例如原来是/opt/pgsql/lib  
+  
+更换主目录后，你的lib可能会放到/opt/pg/lib/postgresql这里去。  
+  
+这个最容易出问题的在extension中。例如：  
+  
+  
+src/contrib/pg_stat_statements/Makefile  
+  
+```  
+ifdef USE_PGXS  
+PG_CONFIG = pg_config  
+PGXS := $(shell $(PG_CONFIG) --pgxs)  
+include $(PGXS)  
+else  
+subdir = contrib/pg_stat_statements  
+top_builddir = ../..  
+include $(top_builddir)/src/Makefile.global  
+include $(top_srcdir)/contrib/contrib-global.mk  
+endif  
+```  
+  
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