今天在 ubuntu 中了招，Makefile 中這樣寫：
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; html-script: false ] g++ -Wall -lcrypto $^ -o $@ |
結果一直顯示錯誤：
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; html-script: false ] undefined reference to `ERR_load_crypto_strings' undefined reference to `OPENSSL_add_all_algorithms_noconf' undefined reference to `OPENSSL_config' |
檢查了 libssl-dev 有安裝，也跑去 /usr/lib 建立一些 link，但是問題都沒有解決。
最後原因是這個：
The –as-needed option also makes the linker sensitive to the ordering of libraries on the command-line. You may need to move some libraries later in the command-line, so they come after other libraries or files that require symbols from them.
Ubuntu 自 11.04 後，預設會將 –as-needed 選項打開，所以參數的順序突然變得很重要了，改成這樣就可以了：
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; html-script: false ] g++ $^ -o $@ -Wall -lcrypto |
參考資料:
https://wiki.ubuntu.com/NattyNarwhal/ToolchainTransition