I have the following configuration:

• uname -a : Linux 2.6.24.2 i686 GNU/Linux (Ubuntu)
• ruby -v : ruby 1.9.0 (2007-12-25 revision 14709) [i486-linux]
• rails -v : Rails 3.0.0.beta3
• gem -v : 1.3.5
• rake --version : rake, version 0.8.7
• make -v : GNU Make 3.81
• gem env :
  • RUBYGEMS VERSION: 1.3.5
  • RUBY VERSION: 1.9.0 (2007-12-25 patchlevel 0) [i486-linux]
  • INSTALLATION DIRECTORY: /usr/lib/ruby1.9/gems/1.9.0
  • RUBY EXECUTABLE: /usr/bin/ruby1.9
  • EXECUTABLE DIRECTORY: /usr/bin
  • RUBYGEMS PLATFORMS:
  • ruby
  • x86-linux
  • GEM PATHS:
    • /usr/lib/ruby1.9/gems/1.9.0
    • /root/.gem/ruby/1.9.0
  • GEM CONFIGURATION:
    • :update_sources => true
    • :verbose => true
    • :benchmark => false
    • :backtrace => false
    • :bulk_threshold => 1000
  • REMOTE SOURCES:
    • http://gems.rubyforge.org/

And when I try this simple command:

gem install nokogiri

Here is what I get:

# gem install nokogiri
Building native extensions.  This could take a while...
ERROR:  Error installing nokogiri:
        ERROR: Failed to build gem native extension.

/usr/bin/ruby1.9 extconf.rb
checking for iconv.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for libxml/parser.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for libxslt/xslt.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for libexslt/exslt.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for xmlParseDoc() in -lxml2... yes
checking for xsltParseStylesheetDoc() in -lxslt... yes
checking for exsltFuncRegister() in -lexslt... yes
checking for xmlRelaxNGSetParserStructuredErrors()... yes
checking for xmlRelaxNGSetParserStructuredErrors()... yes
checking for xmlRelaxNGSetValidStructuredErrors()... yes
checking for xmlSchemaSetValidStructuredErrors()... yes
checking for xmlSchemaSetParserStructuredErrors()... yes
creating Makefile

make
cc -I. -I/usr/include/libxml2 -I/usr/include -I/usr/include/ruby-1.9.0/i486-linux -I/usr/include/ruby-1.9.0 -I. -DHAVE_XMLRELAXNGSETPARSERSTRUCTUREDERRORS -DHAVE_XMLRELAXNGSETPARSERSTRUCTUREDERRORS -DHAVE_XMLRELAXNGSETVALIDSTRUCTUREDERRORS -DHAVE_XMLSCHEMASETVALIDSTRUCTUREDERRORS -DHAVE_XMLSCHEMASETPARSERSTRUCTUREDERRORS -I/opt/local/include/ -I/opt/local/include/libxml2 -I/opt/local/include  -D_FILE_OFFSET_BITS=64  -fPIC -fno-strict-aliasing -g  -fPIC   -g -DXP_UNIX -O3 -Wall -Wcast-qual -Wwrite-strings -Wconversion -Wmissing-noreturn -Winline  -o xml_document_fragment.o -c xml_document_fragment.c
In the included file starting at ./nokogiri.h:75,
          From ./xml_document_fragment.h:4,
          From xml_document_fragment.c:1:
./xml_document.h:5:16: error: st.h : No file or folder with this type
make: *** [xml_document_fragment.o] Error 1


Gem files will remain installed in /usr/lib/ruby1.9/gems/1.9.0/gems/nokogiri-1.4.1 for inspection.
Results logged to /usr/lib/ruby1.9/gems/1.9.0/gems/nokogiri-1.4.1/ext/nokogiri/gem_make.out

The "gem_make.out" file contains the exact same information as described above.

If I try with another gem:

gem install gherkin

Here is what I get:

u# gem install gherkin
Building native extensions.  This could take a while...
ERROR:  Error installing gherkin:
        ERROR: Failed to build gem native extension.

/usr/bin/ruby1.9 extconf.rb
checking for main() in -lc... yes
creating Makefile

make
cc -I. -I/usr/include/ruby-1.9.0/i486-linux -I/usr/include/ruby-1.9.0 -I. -D_FILE_OFFSET_BITS=64  -fPIC -fno-strict-aliasing -g  -fPIC   -o gherkin_lexer_ar.o -c gherkin_lexer_ar.c
/Users/aslakhellesoy/scm/gherkin/tasks/../ragel/i18n/ar.c.rl:11:16: erreur: re.h : Aucun fichier ou dossier de ce type
make: *** [gherkin_lexer_ar.o] Erreur 1


Gem files will remain installed in /usr/lib/ruby1.9/gems/1.9.0/gems/gherkin-1.0.30 for inspection.
Results logged to /usr/lib/ruby1.9/gems/1.9.0/gems/gherkin-1.0.30/ext/gherkin_lexer_ar/gem_make.out

In fact whenever I try to install a gem with native extension, I get the same type of error.

Would that ring a bell to anyone?