gdb正在跳过线路 [英] gdb is jumping over lines
问题描述
我在理解gdb时遇到了一些问题。
我有一个主要功能，我自己写了这个主要功能。
在这个main中的一些行，调用库中的一些函数，我认为库名不重要，但它是tesseract-ocr。
我的行主要调用一个函数，构造函数在这里：
choiceItr = new tesseract :: ChoiceIterator（itr）;
我在gdb的上面放置了一个断点，然后运行，当它停在那条线上时使用step命令进入该函数。
以下是调用的库函数：
ChoiceIterator :: ChoiceIterator（const ResultIterator& result_it）{
ASSERT_HOST（result_it.it _-> word（）！= NULL）;
tesseract_ = result_it.tesseract_;
PAGE_RES_IT res_it（* result_it.it_）;
WERD_CHOICE * best_choice = res_it.word（） - > best_choice;
BLOB_CHOICE_LIST_CLIST * choices = best_choice-> blob_choices（）;
if（choices！= NULL）{
BLOB_CHOICE_LIST_C_IT blob_choices_it（choices）;
for（int blob = 0; blob< result_it.blob_index_; ++ blob）
blob_choices_it.forward（）;
choice_it_ =新的BLOB_CHOICE_IT（blob_choices_it.data（））;
choice_it _-> mark_cycle_pt（）;
} else {
choice_it_ = NULL;
$ / code> 然后我使用gdb的next
这里是我的gdb控制台：
断点1 ，pixsOfOneWord（langString = 0x8049e7cklm，
imageString = 0x8049e71paket2.tif，outputData = 0x8049c7b，
datapathString = 0x8049e6f。）at deneme234.cpp：161
161 choiceItr = new tesseract :: ChoiceIterator（itr）;
（gdb）步骤
tesseract :: ChoiceIterator :: ChoiceIterator（this = 0x819e6f0，result_it = ...）
在resultiterator.cpp中：234
234 choice_it_ = new BLOB_CHOICE_IT blob_choices_it.data（））;
（gdb）next
225 ASSERT_HOST（result_it.it _-> word（）！= NULL）;
（gdb）list
220返回它_-> word（） - > box_word-> BlobPosition（blob_index_）== SP_DROPCAP;
221返回false;
222}
223
224 ChoiceIterator :: ChoiceIterator（const ResultIterator& result_it）{
225 ASSERT_HOST（result_it.it _-> word（）！= NULL）;
226 tesseract_ = result_it.tesseract_;
227 PAGE_RES_IT res_it（* result_it.it_）;
228 WERD_CHOICE * best_choice = res_it.word（） - > best_choice;
229 BLOB_CHOICE_LIST_CLIST * choices = best_choice-> blob_choices（）;
（gdb）next
278} //命名空间tesseract。
（gdb）next
226 tesseract_ = result_it.tesseract_;
（gdb）next
278} //命名空间tesseract。
（gdb）next
226 tesseract_ = result_it.tesseract_;
（gdb）next
230 if（choices！= NULL）{
（gdb）
，您可以看到，
tesseract_ = result_it.tesseract_;
行已被调用两次，为什么？
PAGE_RES_IT res_it（* result_it.it_）;
WERD_CHOICE * best_choice = res_it.word（） - > best_choice;
BLOB_CHOICE_LIST_CLIST * choices = best_choice-> blob_choices（）;
当我下一个，上面的行没有被调用时，为什么？
感谢您的宝贵意见。
调试符号（很可能是 -g -O2 ，这是Linux版本的默认设置）。
调试优化代码有点难，因为控制流优化会导致代码跳来跳去，一些变量会变成<优化出> 等。
您可以使用 CXXFLAGS = -g -O0 重建库，或者您可以学习使用优化进行调试。
后者是一种非常有用的技巧，因为很多时候你的程序只会在优化模式下崩溃，你必须在该模式下调试它。 / p>
i have some problems on understanding gdb.
i have a main function, i wrote this main function on myself.
Some lines in this main, call some functions in a library, i think library name is not important but it is tesseract-ocr.
my line in main which call a function, a constructor is here:
choiceItr = new tesseract::ChoiceIterator(itr);
i put a break point at gdb on above line, and run, when it stops on that line i use step command to go into the function.
Here is the library function who is called:
ChoiceIterator::ChoiceIterator(const ResultIterator& result_it) {
ASSERT_HOST(result_it.it_->word() != NULL);
tesseract_ = result_it.tesseract_;
PAGE_RES_IT res_it(*result_it.it_);
WERD_CHOICE* best_choice = res_it.word()->best_choice;
BLOB_CHOICE_LIST_CLIST* choices = best_choice->blob_choices();
if (choices != NULL) {
BLOB_CHOICE_LIST_C_IT blob_choices_it(choices);
for (int blob = 0; blob < result_it.blob_index_; ++blob)
blob_choices_it.forward();
choice_it_ = new BLOB_CHOICE_IT(blob_choices_it.data());
choice_it_->mark_cycle_pt();
} else {
choice_it_ = NULL;
}
}
then i use "next" command of gdb to walk in function.
here is my gdb console:
Breakpoint 1, pixsOfOneWord (langString=0x8049e7c "klm",
imageString=0x8049e71 "paket2.tif", outputData=0x8049c7b,
datapathString=0x8049e6f ".") at deneme234.cpp:161
161 choiceItr = new tesseract::ChoiceIterator(itr);
(gdb) step
tesseract::ChoiceIterator::ChoiceIterator (this=0x819e6f0, result_it=...)
at resultiterator.cpp:234
234 choice_it_ = new BLOB_CHOICE_IT(blob_choices_it.data());
(gdb) next
225 ASSERT_HOST(result_it.it_->word() != NULL);
(gdb) list
220 return it_->word()->box_word->BlobPosition(blob_index_) == SP_DROPCAP;
221 return false;
222 }
223
224 ChoiceIterator::ChoiceIterator(const ResultIterator& result_it) {
225 ASSERT_HOST(result_it.it_->word() != NULL);
226 tesseract_ = result_it.tesseract_;
227 PAGE_RES_IT res_it(*result_it.it_);
228 WERD_CHOICE* best_choice = res_it.word()->best_choice;
229 BLOB_CHOICE_LIST_CLIST* choices = best_choice->blob_choices();
(gdb) next
278 } // namespace tesseract.
(gdb) next
226 tesseract_ = result_it.tesseract_;
(gdb) next
278 } // namespace tesseract.
(gdb) next
226 tesseract_ = result_it.tesseract_;
(gdb) next
230 if (choices != NULL) {
(gdb)
as you can see,
tesseract_ = result_it.tesseract_;
line has been called two times, why?
PAGE_RES_IT res_it(*result_it.it_);
WERD_CHOICE* best_choice = res_it.word()->best_choice;
BLOB_CHOICE_LIST_CLIST* choices = best_choice->blob_choices();
also when i "next", above lines was not called, why?
Thanks in advnce.
The library you are stepping into has been built with optimization and debug symbols (most likely -g -O2, which is the default for Linux builds).
Debugging optimized code is somewhat hard, as control flow optimization causes the code to "jump around", some variables become "<optimized out>", etc.
You can rebuild the library with CXXFLAGS = -g -O0, or you can learn to debug with optimization on.
The latter is a very useful skill, as many times your program will only crash in optimized mode, and you'll have to debug it in that mode anyway.
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