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I came across this piece of advice on the Google's tcmalloc documentation page.

You can use TCMalloc in applications you didn't compile yourself, by using LD_PRELOAD:

$ LD_PRELOAD="/usr/lib/libtcmalloc.so"

LD_PRELOAD is tricky, and we don't necessarily recommend this mode of usage.

Why do they discourage LD_PRELOAD? Is something inherently wrong with it? Is normal linking more robust? How?

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Sam
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  • Well the documentation is suggesting one way of doing something, but they don't want people to go using "LD_PRELOAD" for . –  Dec 05 '14 at 08:38
  • Those bad reasons are what I want to understand. They only say it's tricky – Sam Dec 05 '14 at 08:57

2 Answers2

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When using LD_PRELOAD, the tcmalloc implementation will be used for any child process as well which may not be what you want.

ysdx
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In addition to ysdx' answer, the value of LD_PRELOAD will also be ignored (for good reasons) for setuid()ed programs.

Depending on the use-case, this might be undesirable. For example, you cannot write a shell script wrapper that exports LD_PRELOAD and then executes the actual program.

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5gon12eder
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