docs: Add more info to the internal design

esp_modem/docs/internal_desing.md

@@ -2,11 +2,58 @@
 
 ## Design decisions
 
-* Use C++ (lambdas) wit C API
+* Use C++ (lambdas, templates) with additional C API
+  
+  | esp-modem in C | esp-modem in C++ |
+  |----------------|---------------|
+```
+    +2282
+    -3908
+```
+
 * Use exceptions (implement nothrow? possibly using `assert()`)
+
+| exceptions off | exceptions on |
+|----------------|---------------|
+```
+Difference is counted as <CURRENT> - <REFERENCE>, i.e. a positive number means that <CURRENT> is larger.
+Total sizes of <CURRENT>:                                                 <REFERENCE>     Difference
+ DRAM .data size:   10996 bytes                                                 10996
+ DRAM .bss  size:   12552 bytes                                                 12488            +64
+Used static DRAM:   23548 bytes ( 157188 available, 13.0% used)                 23484            +64 (    -64 available,      +0 total)
+Used static IRAM:   54145 bytes (  76927 available, 41.3% used)                 54093            +52 (    -52 available,      +0 total)
+      Flash code:  603979 bytes                                                595551          +8428
+    Flash rodata:  187772 bytes                                                177852          +9920
+Total image size:~ 869444 bytes (.bin may be padded larger)                    850980         +18464
+```
+| exceptions on | RTTI on |
+|----------------|---------------|
+```
+Total sizes of <CURRENT>:                                                 <REFERENCE>     Difference
+ DRAM .data size:   10996 bytes                                                 10996
+ DRAM .bss  size:   12552 bytes                                                 12552
+Used static DRAM:   23548 bytes ( 157188 available, 13.0% used)                 23548                (     +0 available,      +0 total)
+Used static IRAM:   54145 bytes (  76927 available, 41.3% used)                 54145                (     +0 available,      +0 total)
+      Flash code:  605331 bytes                                                603979          +1352
+    Flash rodata:  196788 bytes                                                187772          +9016
+Total image size:~ 879812 bytes (.bin may be padded larger)                    869444         +10368
+```
 * Initializes and allocates in the constructor (might throw)
+  - easier code with exceptions ON, with exceptions OFF alloc/init failures are not treated as runtime error (program aborts)
 * Implements different devices with template specialization
-* Specific device abstraction overrides methods, but does not use virtual function dispatch (modeled as `DCE<SpecificModule>`)
+  - Specific device abstraction overrides methods, but does not use virtual function dispatch (modeled as `DCE<SpecificModule>`)
+  - Use cases: Implement a minimal device (ModuleIf), add new AT commands (oOnly in compile time).
+  - Possibly use Module with DTE only (no DCE, no Netif) for sending AT commands without network
+  
+Example:
+```
+class SIM7600: public GenericModule {
+    using GenericModule::GenericModule;
+public:
+    command_result get_module_name(std::string& name); // overrides, but is no virtual
+};
+```
+method `get_module_name()` reimplements the *same* method in `GenericModule`
 
 ## DCE collaboration model
 

esp_modem/private_include/exception_stub.hpp

@@ -7,7 +7,7 @@
 
 #ifdef CONFIG_COMPILER_CXX_EXCEPTIONS
 #define TRY_CATCH_RET_NULL(block) \
-    try { block }  \
+    try { block                   \
     } catch (std::bad_alloc& e) { \
         ESP_LOGE(TAG, "Out of memory"); \
         return nullptr; \

esp_modem/src/esp_modem_api.cpp

@@ -11,6 +11,8 @@
 
 struct PdpContext;
 
+static const char *TAG = "modem_api";
+
 std::shared_ptr<DTE> create_uart_dte(const esp_modem_dte_config *config)
 {
     TRY_CATCH_RET_NULL(