这个问题围绕 SO 有很多变化，但似乎没有一个能解决我的问题。

我正在运行 OSX Lion (10.7.3)。安装了最新的 XCode。

我使用来自 postgresapp.com 的 Postgres.app 包安装了 Postgres。

但是当我尝试安装 pg gem 时，我失败了:

$ gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/MacOS/bin/pg_config
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

        /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/bin/ruby extconf.rb --with-pg-config=/Applications/Postgres.app/Contents/MacOS/bin/pg_config
Using config values from /Applications/Postgres.app/Contents/MacOS/bin/pg_config
checking for libpq-fe.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
    --with-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/bin/ruby
    --with-pg
    --without-pg
    --with-pg-dir
    --without-pg-dir
    --with-pg-include
    --without-pg-include=${pg-dir}/include
    --with-pg-lib
    --without-pg-lib=${pg-dir}/lib
    --with-pg-config
/Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:970:in `block in find_header'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
    from /Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:969:in `find_header'
    from extconf.rb:40:in `<main>'


Gem files will remain installed in /Users/disaacs/.rvm/gems/ruby-1.9.3-p125/gems/pg-0.13.2 for inspection.
Results logged to /Users/disaacs/.rvm/gems/ruby-1.9.3-p125/gems/pg-0.13.2/ext/gem_make.out

/Applications/Postgres.app/Contents/MacOS/bin/pg_config 命令的输出是:

$ /Applications/Postgres.app/Contents/MacOS/bin/pg_config
BINDIR = /Applications/Postgres.app/Contents/MacOS/bin
DOCDIR = /Applications/Postgres.app/Contents/MacOS/share/doc
HTMLDIR = /Applications/Postgres.app/Contents/MacOS/share/doc
INCLUDEDIR = /Applications/Postgres.app/Contents/MacOS/include
PKGINCLUDEDIR = /Applications/Postgres.app/Contents/MacOS/include
INCLUDEDIR-SERVER = /Applications/Postgres.app/Contents/MacOS/include/server
LIBDIR = /Applications/Postgres.app/Contents/MacOS/lib
PKGLIBDIR = /Applications/Postgres.app/Contents/MacOS/lib
LOCALEDIR = /Applications/Postgres.app/Contents/MacOS/share/locale
MANDIR = /Applications/Postgres.app/Contents/MacOS/share/man
SHAREDIR = /Applications/Postgres.app/Contents/MacOS/share
SYSCONFDIR = /Applications/Postgres.app/Contents/MacOS/etc
PGXS = /Applications/Postgres.app/Contents/MacOS/lib/pgxs/src/makefiles/pgxs.mk
CONFIGURE = '--prefix=/Users/mattt/Code/heroku/Postgres/Postgres/Vendor/postgres' '--enable-thread-safety' '--with-openssl' '--with-gssapi' '--with-bonjour' '--with-krb5' '--with-libxml' '--with-libxslt' '--with-ossp-uuid' '--with-perl' '--with-python'
CC = gcc
CPPFLAGS = -I/usr/include/libxml2
CFLAGS = -O2 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wformat-security -fno-strict-aliasing -fwrapv
CFLAGS_SL = 
LDFLAGS = -Wl,-dead_strip_dylibs
LDFLAGS_EX = 
LDFLAGS_SL = 
LIBS = -lpgport -lxslt -lxml2 -lssl -lcrypto -lgssapi_krb5 -lz -lreadline -lm 
VERSION = PostgreSQL 9.1.3

所有这些设置似乎都是正确的，除了 CONFIGURE 变量(它似乎指的是其他计算机——我没有名为 mattt 的用户)。

mkmf.log文件的内容是

"/usr/bin/gcc-4.2 -o conftest -I/Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/x86_64-darwin10.8.0 -I/Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/backward -I/Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1 -I. -I/Users/disaacs/.rvm/usr/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -I/Applications/Postgres.app/Contents/MacOS/include  -O3 -ggdb -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wshorten-64-to-32 -Wimplicit-function-declaration  -fno-common -pipe conftest.c  -L. -L/Users/disaacs/.rvm/rubies/ruby-1.9.3-p125/lib -L/Users/disaacs/.rvm/usr/lib -L. -L/usr/local/lib -L/Applications/Postgres.app/Contents/MacOS/lib     -lruby.1.9.1  -lpthread -ldl -lobjc "
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: int main() {return 0;}
/* end */

如有任何建议，我们将不胜感激。

我查看了 extconf.rb 文件，经过一些调试我发现它是对

find_header ('libpq-fe.h')

那是失败的。不是因为 libpq-fe.h 不存在，而是因为 find_header 方法本身失败了。我尝试使用 irb 运行 find_header，但得到了同样的错误:

$ irb
1.9.3-p125 :001 > require 'mkmf'
 => true 
1.9.3-p125 :002 > find_header 'libpq-fe.h'
checking for libpq-fe.h... RuntimeError: The compiler failed to generate an executable file.
You have to install development tools first.

编辑:

发现我的电脑一定比我想象的还要笨。我正在为另一个项目进行捆绑安装，我在安装 sqlite3 gem 时遇到了非常相似的失败。

checking for sqlite3.h... *** extconf.rb failed ***

我过去从未遇到过 sqlite3 gem 的问题。

最佳答案

终于找到问题的原因了!虽然我仍然不确定这个问题是如何产生的。

查看我的安装命令失败时创建的 mkmf.log 文件的内容(请参阅我的原始帖子)。它记录了运行以下命令的尝试

/usr/bin/gcc-4.2 ...and so on...

我的系统上没有/usr/bin/gcc-4.2。有一个 gcc，符号链接(symbolic link)到 llvm-gcc-4.2。我的解决方案是创建另一个符号链接(symbolic link)

sudo ln -s llvm-gcc-4.2 gcc-4.2 

创建此链接后，我的 gem install pg 命令正常运行。

我在 Frozen Canuck 博客上的帖子 Error Installing Ruby Gem with C Extension 中找到了这个问题的解决方案.他推测问题可能是由 XCode 的版本冲突引起的。不管是什么原因，我永远的感谢!

关于ruby - gem install pg 不适用于 OSX Lion，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10344821/