tmux with C-shell (tcsh) alias are lost - shell

Question

I am running tmux (version 1.9a) on a Mac OS X 10.6.8 with iTerm 2.
My default shell is tcsh, and I have several alias (and path, environment variables) defined in my .tcshrc file.
The problem is that all the alias are not defined when I run tmux, although I set tmux to run with the tcsh shell by default.
Addition: On the other hand the environment variables set in my .tcshrc are correctly passed in tmux. It seems a problem related just to alias...
Below my .tmux.conf
# copy and paster
set-option -g default-command "reattach-to-user-namespace -l tcsh"
# Define the default shell
set-option -g default-shell /bin/tcsh
# Avoid problems with alias defined in .tcshrc
set-option -g default-command $SHELL
set-option -g default-command "source .tcshrc"
# look good
set -g default-terminal "screen-256color"
set -g prefix C-a
unbind C-b
bind C-a send-prefix
# a mouse
set -g mode-mouse on
setw -g mouse-select-window on
setw -g mouse-select-pane on
# # Scroll History
set -g history-limit 30000
# Count sessions start at 1
set -g base-index 1
# act like vim
setw -g mode-keys vi
bind h select-pane -L
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R
bind-key -r C-h select-window -t :-
bind-key -r C-l select-window -t :+
unbind [
bind -t vi-copy v begin-selection
bind -t vi-copy y copy-selection
# after copying to a tmux buffer, hit y again to copy to clipboard
bind y run "tmux save-buffer - | reattach-to-user-namespace pbcopy"
bind N swap-window -t +1
bind P swap-window -t -1
# Reload .tmux.conf
#bind R source-file ~/.tmux.conf \; display-message " Config reloaded.."
# Hit [PREFIX]-R to reorder windows (i..e from 1-4-7-9 to 1-2-3-4 keeping the right order)
bind R \
set -g renumber-windows on\; \
new-window\; kill-window\; \
set -g renumber-windows off\; \
display-message "Windows reordered..."
# Rename your terminals
set -g set-titles on
set -g set-titles-string '#(whoami)::#h::#(curl ipecho.net/plain;echo)'
# Status bar customization
# Set status bar
set -g status-justify left
set -g status-bg black
set -g status-fg white
set-option -g status-interval 5
set -g status-right-length 150
set -g status-left ""
set -g status-right "#[fg=green] %m-%d-%Y %H:%M #(whoami)#minimul.com " # Add space so I can see Growl notifications in full-screen mode
# Rather than constraining window size to the maximum size of any client
# connected to the *session*, constrain window size to the maximum size of any
# client connected to *that window*. Much more reasonable.
setw -g aggressive-resize on
# Allows us to use '<prefix>-a' <command> to send commands to a TMUX session inside
# another TMUX session
bind-key a send-prefix
# Highlight active window
set-window-option -g window-status-current-bg red

Answer 1

Apparently the issue was solved by keeping the line
set-option -g default-command "reattach-to-user-namespace -l tcsh"
while erasing the lines
# Define the default shell
set-option -g default-shell /bin/tcsh
# Avoid problems with alias defined in .tcshrc
set-option -g default-command $SHELL
set-option -g default-command "source .tcshrc"
And restarting iTerm2 (no source or rehash did the job).

Answer 2

This would be because when you launch a standard shell from the terminal, it's a login shell, but with the option you've set for tmux, it's just an additional shell.
This line:
set-option -g default-command $SHELL
actually causes it to launch as a non-login shell. You've probably got some code blocked off with:
if($?loginsh) then
...
endif
which means that it doesn't get invoked in that case.
If you change the option to:
set-option -g default-command "$SHELL -l"
It will act like a login shell; alternatively remove the default-command, and in that case it will invoke the default shell as a login shell, which should have the same effect.
As an attempt at debugging this I started with a from-scratch .tcshrc containing:
echo tcshrc
if($?loginsh) then
echo login
endif
if($?prompt) then
echo prompt
endif
with set-option -g default-command "" (the default) I saw:
tcshrc
login
prompt
with set-option -g default-command "$SHELL" I see:
tcshrc
tcshrc
prompt
with set-option -g default-command "$SHELL -l" I see:
tcshrc
tcshrc
login
prompt
with set-option -g default-command "reattach-to-user-namespace tcsh" I see:
tcshrc
tcshrc
prompt
with set-option -g default-command "reattach-to-user-namespace -l tcsh" I see:
tcshrc
tcshrc
login
prompt