libcurl-thread.3: Warn memory functions must be thread safe

allows the application to set callbacks to replace the otherwise used internal

memory functions.

This man page only adds documentation for the callbacks, see the

\fIcurl_global_init(3)\fP man page for all the rest. When you use this

function, all callback arguments must be set to valid function pointers.

When you use this function, all callback arguments must be set to valid

function pointers. \fBIf you are using libcurl with multiple threads the

callback replacement functions must be thread safe.\fP

The prototypes for the given callbacks should match these:

.IP "void *malloc_callback(size_t size);"

To replace strdup()

.IP "void *calloc_callback(size_t nmemb, size_t size);"

To replace calloc()

.RE

This function is otherwise the same as \fIcurl_global_init(3)\fP, please refer

to that man page for documentation.

.SH "CAUTION"

Manipulating these gives considerable powers to the application to severely

screw things up for libcurl. Take care!

\fBcurl_global_* functions.\fP These functions are not thread safe. If you are

using libcurl with multiple threads it is especially important that before use

you call \fIcurl_global_init(3)\fP to explicitly initialize the library and its

dependents, rather than rely on the "lazy" fail-safe initialization that takes

place the first time \fIcurl_easy_init(3)\fP is called. For an in-depth

explanation refer to \fIlibcurl(3)\fP section \fBGLOBAL CONSTANTS\fP.

you call \fIcurl_global_init(3)\fP or \fIcurl_global_init_mem(3)\fP to

explicitly initialize the library and its dependents, rather than rely on the

"lazy" fail-safe initialization that takes place the first time

\fIcurl_easy_init(3)\fP is called. For an in-depth explanation refer to

\fIlibcurl(3)\fP section \fBGLOBAL CONSTANTS\fP.

\fBMemory functions.\fP These functions, provided either by your operating

system or your own replacements, must be thread safe. You can use

\fIcurl_global_init_mem(3)\fP to set your own replacement memory functions.

\fICURLOPT_DNS_USE_GLOBAL_CACHE(3)\fP is not thread-safe.