Appends the characterc to the output character sequence.

Ifc is the end-of-file indicator (traits::eq_int_type(c, traits::eof())==true), then there is no character to append. The function does nothing and returns an unspecified value other thantraits::eof().

Otherwise, if the output sequence has a write position available or this function can successfully make a write position available, then callssputc(c) and returnsc.

This function can make a write position available if thestd::stringbuf is open for output ((mode& ios_base::out)!=0): in this case, it reallocates (or initially allocates) the buffer big enough to hold the entire current buffer plus at least one more character. If thestd::stringbuf is also open for input ((mode& ios_base::in)!=0), thenoverflow also increases the size of the get area by movingegptr() to point just past the new write position.

[edit]Parameters

[edit]Return value

Traits::eof() to indicate failure,c if the characterc was successfully appended, or some value other thanTraits::eof() if called withTraits::eof() as the argument.

[edit]Notes

This function is different from a typicaloverflow() which moves the contents of the buffer to the associated character sequence because for astd::basic_stringbuf, the buffer and the associated sequence are one and the same.

[edit]Example

#include <sstream>#include <iostream> struct mybuf:std::stringbuf{    mybuf(conststd::string& new_str,std::ios_base::openmode which=std::ios_base::in|std::ios_base::out):std::stringbuf(new_str, which){}     int_type overflow(int_type c=EOF) override{std::cout<<"stringbuf::overflow('"<<char(c)<<"') called\n"<<"Before: size of get area: "<< egptr()- eback()<<'\n'<<"        size of put area: "<< epptr()- pbase()<<'\n';         int_type ret= std::stringbuf::overflow(c); std::cout<<"After : size of get area: "<< egptr()- eback()<<'\n'<<"        size of put area: "<< epptr()- pbase()<<'\n'; return ret;}}; int main(){std::cout<<"read-write stream:\n";    mybuf sbuf("   ");// read-write streamstd::iostream stream(&sbuf);    stream<<1234;std::cout<< sbuf.str()<<'\n'; std::cout<<"\nread-only stream:\n";    mybuf ro_buf("   ",std::ios_base::in);// read-only streamstd::iostream ro_stream(&ro_buf);    ro_stream<<1234; std::cout<<"\nwrite-only stream:\n";    mybuf wr_buf("   ",std::ios_base::out);// write-only streamstd::iostream wr_stream(&wr_buf);    wr_stream<<1234;}

read-write stream:stringbuf::overflow('4') calledBefore: size of get area: 3        size of put area: 3After : size of get area: 4        size of put area: 5121234 read-only stream:stringbuf::overflow('1') calledBefore: size of get area: 3        size of put area: 0After : size of get area: 3        size of put area: 0 write-only stream:stringbuf::overflow('4') calledBefore: size of get area: 0        size of put area: 3After : size of get area: 0        size of put area: 512

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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