描述
ABB 8039200
技巧7 – 避免易失存儲器分配
不習(xí)慣在資源有限環(huán)境下工作的工程師,可能會試圖使用其編程語言的特性,這種語言讓他們可以使用易失存儲器分配。畢竟,這是一種常在計算器系統(tǒng)中使用的技術(shù),在計算器系統(tǒng)中,只有在有必要時,內(nèi)存才會被分配。例如,以C開發(fā)時,工程師可能傾向于使用malloc來分配在堆(heap)上的空間。有一個操 作會執(zhí)行,一旦完成,可以使用free將被分配的內(nèi)存返回,以便堆的使用。
在資源受限的系統(tǒng),這可 能是一場災(zāi)難!使用易失存儲器分配的其中一個問題是,錯誤或不當(dāng)?shù)募夹g(shù)可能會導(dǎo)致內(nèi)存泄漏或內(nèi)存碎片。如果出現(xiàn)這些問題時,大多數(shù)的嵌入式系統(tǒng)并沒有 資源或知識來監(jiān)視堆或妥善地處理它。而當(dāng)它們發(fā)生時,如果應(yīng)用程序提出對空間的要求,但卻沒有所請求的空間可以使用,會發(fā)生什么事呢?
使用易失存儲器分配所產(chǎn)生的問題是很復(fù)雜的,要妥善處理這些問題,可以說是一個噩夢!一種替代的方法是,直接以靜態(tài)的方式,簡化內(nèi)存的分配。例如,只要在 程序中簡單地建立一個大小為256字節(jié)長的緩沖區(qū),而不是經(jīng)由malloc請求這樣大小的內(nèi)存緩沖區(qū)。此一分配的內(nèi)存可在整個應(yīng)用程序的生命周期期 間保持,且不會有堆或內(nèi)存碎片問題方面的顧慮。
這些都只是一些可以讓開發(fā)人員開始建立更可靠嵌入式系統(tǒng)的方法。另外還有很多其他技術(shù),例如利用良好的編碼標(biāo)準(zhǔn)、位翻轉(zhuǎn)的監(jiān)測、執(zhí)行數(shù)組和指針邊界檢查,及使用斷言等。所有這些技術(shù)都是讓設(shè)計者可以開發(fā)出可靠性更高嵌入式系統(tǒng)的秘訣。
產(chǎn)品承諾:
保?證?全新原裝進(jìn)口,
保?證?安全準(zhǔn)時發(fā)貨,
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優(yōu)勢價格,大量現(xiàn)貨。
主營DCS系統(tǒng)配件
機(jī)器人系統(tǒng)配件
大型伺服系統(tǒng)配件
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